I didn't get a chance to finish it (only has the basis for two attacks, if that...), but here's a boss in the style of the RPG I may or may not one day actually start. You can find the original work here: http://opengameart.org/content/tiki-concept . I only wish I had time to finish it though...

The original tilesets on which this work is based can be found here:

http://opengameart.org/content/lpc-a-shootem-up-complete-graphic-kit

http://opengameart.org/content/lpc-farming-tilesets-magic-animations-and...

http://opengameart.org/content/lpc-skorpios-scifi-sprite-pack

http://opengameart.org/content/road-tile-set

http://opengameart.org/content/chainlink-floor-tiles

http://opengameart.org/content/lpc-colorful-sand-deep-water

http://opengameart.org/content/liberated-pixel-cup-base-assets-sprites-m...

(I hope I didn't miss anything)

Three monsters based off of preexisting concept work on OGA.  Fun stuff, but sprites this detailed at this size are time-eaters for sure.

Graffitiiiiiiiiiiiiiiiiiiiii !

Well, I didn't plan to enter, but I was told I should. ;)

Anyway, these are some mechs rendered from Skorpio's models (original works here and here).

Zombie and Skeleton. Original art work: http://opengameart.org/content/zombies-skeletons

Added walking animations and scaled up to usable with 32x32 tiles.