Nice arena, but I have some tips.
You should make it a glass block enclosed area, as having just plain clay walls around it would both look sad and not the best eye teaser.
If you plan on keeping the walls, then use simple but big decorations to give some personality to the arena.
Make the ground as natural as possible. Make it seem the player is battling for his/her life in the out and open, not some type of simulator.
Definitely decorate “PvP” more graciously and enlarge it. This whole arena is dedicated to PvP, make sure to emphasize that fact.