livlily

Living Lines Library, or Livlily, is a collection of pencil tests, character model sheets, concept art and more, reaching as far back as Dumbo and as far forward as Rio and Puss in Boots. It reaches both short foreign films to full length features, and you can search by animator or movie. Either way, it’s great reference. 

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A couple of aspects that I love about animation are model sheets and concept art.

These are from Atlantis the Lost Empire (2001) (incidentally the first movie that I ever got on DVD) and The Fantastic Mr. Fox (2009).

I got the from the blog of Nagy Péter which can be found here: http://livlily.blogspot.com/2010/11/model-sheets-production-drawings.html

as well as oodles more things like these.