This is too late to be relevant for this tournament, clearly, but I would like to suggest a level based restriction. I've noticed that in the current tournament, some of the levels vary greatly from the levels of the other participants. (The lowest level being 12, while the highest level is 27. 15 levels is a huge gap.) And I was honestly thinking a lower-ish leveled tournament would be a good change of pace.
Another user, although I don't recall who at the moment, also thought a level 1 tournament would be interesting, since it would primarily be relying on traits. Everyone should have a level 1 pet somewhere in their arsenal, so even newer users could participate. Or if that's too low, then perhaps a level 5 tournament?
If wanting to use a decent range of levels, in my opinion, it would be good to not go higher than level 20, and closer to the 10-ish or 15-ish area.