It's definitely a quite unique model, and it does have its charm to it!
The figures look okay; my main problem is the agori (But I know how they can be hard to make with the limitations of LDD) as the proportions of kinda off (big body, small head syndrome) .
Now the actual arena itself, looks very different from cannon! Now, that's not a bad thing; for example, you were able to incorporate many functions and play features into the build.
That said, though,I feel that the model doesn't really evoke the feeling of 'arena' for me; it looks more like a wall/fortress/outpost being attacked by tentacles.
Overall, though, you did a fine job.The model is creative and the mini-figs are neat! I wish you good luck on the contest!