Contributing some boring, basic terrains because I'm just a boring guy I guess:
The Sand Blasts
A flat plain stretching for miles in every direction. The ground here is hard as stone, baked by the sun and hardened over time. A thin layer of dust and sand lies on the ground, ready to be kicked up by any sudden movement or gust of wind. Every here and there is a crater, easily located by the blackened char marks around it. These craters are easy enough for a human-sized combatant to hop in or out of, and can be used for cover if you crouch. Seems like the two fighters weren't the first ones to have a battle here...
The Wilder Woods
A dense forest of lush greenery, though oddly devoid of any animals. The trees are packed close together, making the whole place a bit claustrophobic, and most of the trees' branches are strong enough to support a fighter's weight. Sun trickles in through holes in the canopy, enough to light up most of the place while still leaving plenty of shadows to hide in. The ground is uneven and teeming with roots, vines, and other life, so watch your step. And be careful: the woods are alive, and not in the way you might think. When you look away, they change, so don't expect to leave a hiding spot and then return to it later. Whether the woods are really shifting, or if it's just a trick of the mind, we don't know. But if the woods are alive, they have an agenda. If the fighters lose track of each other, they'll find themselves brought back together sooner than you might expect.
The Empty Fields
An idyllic field blanketed by short, soft grass. Here and there are a few gentle slopes, but most everywhere is flat enough ground to fight on without a problem. Large gray stones lie planted in the ground every few hundred feet, give or take -- they're large enough to be used as cover by human-sized fighters, if you're willing to crouch, at least. Aside from the rocks on the ground and the clouds in the sky, there's not much else here. But isn't that enough?
The World Arena
Once the site of a great tournament, now the site of a match of another. On the ground is a massive stone disc, a couple feet high and a couple hundred feet in diameter. Another fifty feet or so from the disc are the stands, where people used to sit to watch the tournament -- but there aren't any people here anymore. The disc itself is solid, but can be damaged by powerful fighters. The stands are less solid, only made to withstand rowdy crowds, so tread lightly. Fighters who leave the arena will find an empty desert for miles in every direction; guess it makes sense not to build a place like this near anything important...
The Broken Pieces
A bunch of blackish-blue, somewhat important looking stones floating in a void, as if it was the most natural thing in the world. The stones are perfectly flat on top but rough and uneven on the bottom, like tiny mountains, cut from the earth and flipped over. The stones are various sizes, with fighters starting on opposite ends of the biggest one, over a hundred feet long and a bit less wide. From there, athletic fighters, or ones who can fly, can move to the other islands, which float all around the larger one -- some floating above it, some below it, and some about level with it. The stones are tougher than stone has any right to be, but the strongest fighters can still smash 'em, if they want to. But no amount of force or weight will ever be able to force one of the islands up or down; they're stuck there, in the middle of nowhere.
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"The courtroom is the garden of holy judgment. Those with lechery in their hearts should leave this sanctuary at once!" ~Franziska von Karma