Gonna clean up the code but this is the basic outline.
Index of Categories with big thumbs, leading to the category page with small thumbs, and those link to posts.
thumb index of categories
http://pics.fris.net
thumb index of the category page
http://pics.fris.net/category/anal
post page
http://pics.fris.net/cute-kitty.html
note: the styling is very minimal, since this only took 10 mins to do, uses 1 plugin, which im gonna remove (the one that does the category images)
ill put this on github or my site if you wish to download it.