I share a very small room with my sister, and obviously don’t have much room for an altar. I use most of my space for my Hellenic shrines and altar. I keep my witchy stuff on my shared bedside table. Here is what I use, and how I store/display it. This is element based, but you can use it however you like.
Small Himalayan Rock Salt Lamp - This is a tool I use all the time. It detoxifies my room, and cleanses the space. I feel so much more at ease with it on, like it’s washing everything away!
Crystals - You might want to move these or switch them out depending on what spell you’re doing, as all energy contributes to the working, but while you’re in your room, or even while you’re away, you can leave these here to represent Earth.
Salt - Little packets of salt work, or you can place a bowl with some salt in it on your altar. I use my rock salt lamp.
Dirt - A literal baby jar of dirt works, or you can put a plant on your altar if it’s by a window. I have a succulent!
Earth Imagery - A mini globe would be pretty cool! Or even a little eraser or what not. Having an actual picture of the Earth would be amazing, especially if the clouds were visible, and maybe if it had the sun in the background. Then it could be all encompassing of the elements.
Herbs, Flowers, Plants, etc - As with the crystals, you may want to change these out or put them away during spells, or switch them out. However, they would look really cool as you went with the seasons!
Fossils - I think fossils are awesome Earth representations. They have been in the ground for a very long time! I used to have some really cool fossils I used to represent Earth on my altar.
Tree Slice - Have you ever seen those little wooden slices that come from a tree stump? The ones that definitely had huge roots? Those would be perfect to represent Earth!
Birthday Candles/Tea Lights - You can colour code! These are great for short workings, or even to call the elements. To make these stand up, place them in a bit of clay and let it harden.
Matches - Double whammy here- light your candles and have a representation!
Ash - I used to have volcanic ash, which was perfect. It got spilled, but for the while that I had it, it was awesome. Collect ash from incense, a fire, etc, and use it (just wait for it to cool!!!)
Charcoal - I always thought charcoal looked kinda witchy. I think a dish of it would make a good rep.
Charred Wood - If you have a bonfire, or just so happen to light a piece of wood on fire, you could let it cool and use it for your altar.
Lamp - If you have a secret altar, a little lamp could be an inconspicuous representation for fire, as it does produce light and heat.
Lantern - You can buy super cute mini lanterns at the Dollar Store. I love them, but haven’t gotten one yet. I think they would be fun to use for Fire.
Glass of Water - You can use whatever type of water you’d like; moon water, rose water, purified water, gem elixir; take your pick! Just make sure it doesn’t get moldy and stay moldy. Change it out each day/week.
Sea Shells - You can get these in super small sizes! Or, you can get them big and bulky.
Sea Glass - These little stone-like fragments are so pretty! They look just like crystals, and can be found on the beach or in the store!
Sea Salt - Sea Salt could work to represent Water, especially if you pour it into a seashell or add in sea glass to it. It could be like a little potpourri of water related objects!
Rain Cloud - You can create clouds out of things like stuffing for toys, cotton balls, and sometimes led lights. It could be a fun project, or you can buy one of them off of etsy.
Mermaid Image - I have a mermaid book mark made of metal, and it sits with my other water-related objects. I feel like it adds that feel of majesty to my water representation.
Drift Wood - This is so pretty! The pieces are smooth, have a fun shape, and definitely capture the essence of water!
Sand - If you go to a beach, collect some sand, and place it somewhere on your altar! Be sure to put it in a bowl, though, because it is hard to clean up.
Sea Weed - You can hang this somewhere, or put it directly on your altar. Either way, it looks great.
Coral - If you find some coral, you can place it on your altar. It looks so neat!
Starfishes/Sand Dollars/etc. - These are a little harder to find on the beach, but if you do, place them on your altar.
Wind Chimes - These add a little decoration to your altar, as well as give you an air representaiton. You can even listen for the tinkling of bells to see if any fae are around!
Bells - If you ring a bell, it disperses stagnant energy, and helps to cleanse a space. Having one on your altar is a great way to keep it fresh!
Feathers - This is a pretty obvious one, an oldie but a goodie. If you have some feathers, you can use them, but make sure there are no laws against collecting them in your area. Alternatively, you can use fake ones from a craft store.
Empty Glass or Bottle - Air is all around us. Use that to your advantage!
Dandelion Puff - This is what I immediately think of when I picture the wind. You can collect some puffs and put them in a glass.
Bird’s Nest (fake) - You can buy or make a fake bird’s nest. They look pretty real, and have this awesome rustic naturey vibe to them!
Leaves - They were once high in the sky! Collect them during the fal season or after a storm.
Incense - Another well-known one. You can burn this and use the smoke.
Tornado Making Jar - You know those little jars that you can shake up, and they make a tornado? Those would be a fun water-air duo!
Small Jewelry Box - This can store crystals, herbs, essential oils, etc. I use to use mine to cleanse my crystals becuase it played music!
Multi Colour Light-Up Candle - I found mine at Five Below! It lights up in tons of different colours, but is pretty large. However, it takes up a lot less room than a bunch of different coloured candles.
Your Wand - Having your wand on your altar makes it a sacred, special tool. It will be charged by the witchy items you have there, and will feel natural inn the environment.
A Mini Besom or Real Besom (Broom) - I use a paintbrush as a mini besom, as I can’t have real one. However, it would be nice if I did, and I’d keep it near my altar!
Your Grimoire/Spellbook/BOS/etc - If you aren’t hiding it, you could keep it on your altar!
A Fire-Safe Dish or Cauldron - If you water scry, burn things, or just like to include your cauldron in your spells, you can keep it on your altar.
Incense Tray - Incense can’t be burned without somewhere to place it. Keep your incense holder handy!
Altar Cloth - This ties everything together! It can be switched out for sabbats/festivals/seasons/spells.
Chalice - I’m not Wiccan, but I use the chalice in my workings every once in a while, usually for water-related magic. You can get these beautiful metal ones at antique stores, or regular old wine glasses at the dollar store!
Mortar and Pestle - For practical use and an awesome vibe! You can keep this near your herbs.
Coloured/Enchanted Salts - They display beautifully,and are really good to have on hand.
Spirit Vessels - These can go in their own little corner if you like. They could also be the center of your altar, especially if you work mainly with spirits.
Tarot/Other Cartomancy Cards - Find a nook for your cards to be kept safe and clean. They will be charged by the other objects all around it, which makes it an awesome idea to have on your altar.
Scrying Mirror - Make this the main attraction, or perhaps just a piece of the puzzle. If you have an ornate mirror, it could be a very drawing part of your altar!
Crystal Ball - Like the scrying mirror, it could be a background piece or the focal point.
Runes - If you cast runes, you can keep your bag or box of them on or near your altar.
Other Divination Tools - You cans store these, or just la them throughout your altar. Whatever you choose, having your tools close by will be awesome!
Twig Shapes - You can make sigils out of twigs and hot glue! Add a ribbon or piece of twin in the shape of a loop, and you can hang them above your altar as decoration and as a little energy booster!
Circle (Embroidery Hoop) - I know most people use salt to cast circles, but I actually use an embroidery hoop. I cast one around myself, and one around the items I am working with (ex: what’s in the hoop).
Knife - If you use a ritual or practical knife in your workings, it’s good to have on hand. I can’t have one, but I like my wand better anyway, personally.
Fae Garden - You’ll have to have plenty of sunlight near your altar for this one, but it will definitely be fun to have some Fae living on your altar!
Spell Supplies - Random bits and bobs, like egshells and ribbons, can be kept on your altar as well.