I ran a Dungeon & Dragons arena that I call “Dungeon Ball”. I created a map in Gimp and ran the arena via MapTool. The map has a maze in the middle and goals on the edges. The object of the arena is to take a ball from the center of the map, and carry it to your goal. This is my first maze to post, and the second one I've ever created.
I used GIMP to create the map. I used pattern fills, drop-shadows, etc. But the two things I was most proud of were the maze and the goals.
I used a bump map for the maze. The floors started as a simple slate pattern fill, then added the maze. I drew a control layer of the maze walls (filled in), and applied a Gaussian filter cropped to actual wall boundaries (i.e., removed the halo). I then used this control layer as a bump map on the floor. Then I added drop shadows.
For the goals I wanted the appearance that they were painted on, but faded. I used a gradient to create diagonal stripes, then added an alpha channel for partial transparency. The alpha channel fades near the edges, so the goals fade out.
Finally, to facilitate grid alignment in Maptool, I added a tic-tac-toe board outside the arena.
I have a post on my web site which talks about the arena as a whole, including a little more about game play and how I used Maptool to run the arena.