There are a bunch of rarely used Style tags:

abstract(3)
art_nouveau(9)
icons(1)
illusion(1)
interpreted(5) I'm not even sure what this one is for.
letterboxed(6) Useful, but hardly used.
photomosaic(3) I'm not sure if there are other photomosaics here or not.
pixel(5) I know there are more sprite images on here, but it would take forever to find them.
scanning_artifacts(5) Most crappy scans just get deleted it seems, so this one is kind of redundant.
sprite(1) Same as pixel
text_art(2) Aside from those two images, I haven't seen any other text images here.