Now that you've mentioned Keith's bike I'm curious about where it may have come from. Another memento of his mom? Something that the people who brought Blue to Earth left behind?
Believe it or not someone was just talking to me about this. Credit to dhaarijmens who I… cannot @ for some reason, for this screengrab:
So the poster up behind Hunk’s head, at a glance, would seem to be an advertisement for the bike. Oh, mystery solved, it’s normal Earth technology and Pidge just had coincidentally never seen anything like it before. Pidge… the… science enthusiast. Hm.
So I went deeper.