I started out on a mission to unify the various 32x32 castle tilesets into a consistent, LPC-compatible style, and I got a little carried away. All the castles had something I liked---Zabin's had those great towers with the sloped walls, Evert's had the curved merlons, theidiotmachine's had my favorite color scheme and some really nice shading/details, and Daniel Armstrong's had those great windows and doors. On the other hand, there were things about each of them that I didn't like---Zabin's had a bit too much texture, the castle from the LPC base assets didn't have quite enough, etc. 

So I converted everything to the same palette and then adjusted the shading and details until they looked somewhat consistent. The styles are still different enough that they don't really look great as part of the same building, but they can at least exist in the same world or town. Having them all in the same color let me do a few recolors too, so there's a light and a dark version which maintain the same style but have somewhat different feels. I've tried to make the layout logical and space-efficient, but I've kept the three distinct styles in separate sections so they can be broken apart if necessary. There are some unused tiles marked in green. 

Finally, I added a bunch of architectural features---equilateral arches, rose windows, pinnacles, flying buttresses, crockets and so on which can be sprinkled on to buildings made with any of the sets to give the piece more of a Gothic feel. They can also be used to build churches,  cathedrals, etc.

CC-BY-SA 3.0 was the only license common to all the submissions, but I'm willing to license the whole thing more liberally if the other contributors agree.