-Old star charts. Being a space nerd I'd like something space related that doesn't look like it shoud be hanging over a crib. I could stare at Hubble pictures for hours, but I guess nebulas would just look like random blobs of colour..
-Old maps, with text "here be dragons"...
-Mushrooms. Cute and delightfully phallic.
-Brian Froud-like faeries, goblins and elves. Rather a bit mischevious than sweet.
-Spooky trees would work well as a gothic print. Or just trees and foliage for a mori-inspired look.
-Penguins or puffins would make an adorable sweet print.
-Witches with brooms and cauldrons, maybe with frogs and lizards...
What would you like to see?