First off, great. The artist has great skill not seen much. This is one of the best artworks I've seen on dA. Really good. Even includes the almost never seen snail, giant, and worm. Amazing style. The lighting is weird though. For Lumpy Space Princess, the brightest area is the top right. For Ice King it's the middle right. For the snail, the light is coming from directly above. It's coming on the giant straight on, from the right for Jake, and directly below for Finn. Over all great work, I would suggest working on lighting. Over all, great picture!