I've made somextra based off dead fantasy. 

Like their Tilted Tower,  where you fight as you run down a tilted tower,  I added the catch that you had to stay on the ground so people wouldn't just fly everywhere. Also I based one off of the fight they had in sat or Nadal tornado. 

Another one I've fought in was based on columna that fell if you stepped on them a certain number of times.

My favorite arena was one I created for a four way I hosted. Five black blobs that each combatant could change to suit their need. The fifth was kept the same as a neutral ground. Each round it would randomly change to a different blob. only a few things transferred over from each. 

Actually no, a friend of mine made that one. I just used it for the four way I hosted. It was really popular.