Yeah, game design is hard. I come from a similar place since I am primarily an artist and at least my whole approach is to try to come up with a game where I can stuff as many of the things as I really want to draw as I can. So puzzle games work best for that it seems.
I had one game I made where you have to sort out peoples dreams and the dreams can be almost any sort of image so it seemed like a good enough way to add playability to the whole situation. I think just adding unlockable stuff or a simple story can do a lot, or otherwise it's more similar to wandering in a museum than to playing a game.