Some stages I made and posted at SWF (under my alias Z1gma) a couple months ago.
I thought they might be of use here.
Bowser's Castle: Image explains most of it; The Fire Balls do low/medium damage and knockback, sending ppl straight up.
DK Mine Kart caves: Once in a while a croc comes racing through the stage, sometimes from the left and sometimes from the right. Sometimes he jumps and takes the upper route (the passable platform), and sometimes he simply goes under it. He does medium damage and knockback, and sends ppl up and away.
He moves pretty fast, so stay at your toes.
DK Tree Tops: A neutral stage made up of a Main platform and a smaller, passable platform. The barrel can save your life if you're lucky.
Orange Star HQ: Not sure if it should have hazards or not, since it'd make a pretty good neutral stage as it is.
Anyways, with hazards: Air Forces battle it out in the background, and sometimes missiles and bombs are accidentally fired at the stage.
Also, distant commanders will sometimes activate their CO Power - some of them are:
BLIZZARD: Olaf's power turns the stage into snow and ice for a small period of time, making it slippery.
TYPHOON: Drake's power calls down heavy rain for a small period of time, which decreases players' Jumping Ability.
BLACK WAVE: Hawke's power makes the screen flash with red lightning. Everyone who's hit takes low/medium damage and knockback, and are sent straight up. It's an attack that covers the entire screen, but it's not that hard to avoid if you're aware of it and dodge it in time. Works similar to Shadow's FS.
[Maybe there could be a picture of the commander and the power to come at the bottom of the screen before they're activated, like in the games? With epic quotes, of course.]
Gemini Man Stage: The eggs are breakable, but respawn after some time.
Mario Bros 2: Here's a med-large map. The logs roll down the waterfall like in the game, and you can climb the stalk (if climbing is in 0.9).
Orange Ocean: The red lines show where you can walk, the purple stars shows ledge grabs, and the coconuts are weak hazards that fall down upon beeing hit, doing low damage and knockback, knocking ppl away all so little. They respawn after a small period of time.
Bubble Man Stage: Those red/brown platforms fall down shortly after you step on them only to respawn later on. Robot Crabs fall down from time to time and starts walking until they fall off the stage, doing low/medium damage and knockback, and sends ppl up and away.
Skull Man Stage: The far right platforms are passable, the others are not.
The cannon fires its bouncing projectile from time to time, doing medium/high damage and knockback, sending ppl up and away. The cannon itself does no damage. Not the most competitive stage - use cheap tactics to prevail!