The idea is that a beautiful image is frameable. Everything you need to see is there: It’s everything you want, and it’s very pleasing because there’s no extra information that you don’t get to see. Everything’s in a nice package for you. But sublime art is unframeable: It’s an image or idea that implies that there’s a bigger image or idea that you can’t see: You’re only getting to look at a fraction of it, and in that way it’s both beautiful and scary, because it’s reminding you that there’s more that you don’t have access to. It’s now sort of left the piece itself and it’s become your own invention, so it’s personal as well as being scary as well as being beautiful, which is what I really like about art like that.
There is a BIG, long article about Adventure Time. It’s pretty good.