I recently had the immense honor of doing some pixel art for the webcomic Homestuck. This is one of the sets I did, put together into a mockup of sorts. They appeared in Act 6 Intermission 3 (http://www.mspaintadventures.com/?s=6&p=007163, though beware spoilers and the fact that it won't make any sense unless you have context). It was a huge pleasure to work on Prospit and Derse: their mixture of architecture types, the various and intricate styles and most of all the towering spires have always made them one of my favorite elements of Homestuck.
The individual pieces are viewable here: http://i.imgur.com/Ug9Zh.png These aren't technically tiles so much as elements used by Andrew to make a single map image. He is a very talented man, and definitely made better use of them than I did in this mockup.
Note: I did NOT do the character sprite! That is the work of Amanda H (http://merrigo.tumblr.com/), and is included for scale/context.
Edit: some small changes to the mockup based on comments. Thanks.