Name: self-explanatory
Gender & Age: how much do falling on narrow horizontal sufaces feet first hurt you? And how often do you remember the pain?
Concept

bender,non-bender, which Kingdom you're originally from,what type of bender you are etc.)
Appearance:how pretty are you? Or as the case may be, how much do we wish to look away from Sparky Sparky Boom-Man's ugly cousin?
Personality:how much do you abhor cabbages? Would you kick a Platypusbear when it's down, or do you just go with the flow(that's not an invitation, air benders) and think everything's hunky-dory?
Equipment:your swords, staves, weapons of mass bending supernovas, etc., go here, also go ahead and put anything special, I'm going to assume Waterbenders have at least a personal bending source on their bodies.
Fighting Style: this is really only for the non-bender sheets, so no real reason for benders to have this on their sheets, you've got your bending and the associated martial art I'll assume you're at least proficient in, unless this states otherwise.
And just for reference if you are going to look up your associated martial style, here's a vid that'll at least tell you the name so you can write it for your character. I'd rather have each character to write their combat scenes slightly different from one another.
Bio:guess what? You weren't born yesterday, so you can't be the Avatar, really the only limit I'm imposting. And also, Air Nomad sheets can have their Bison, but I'm imposing a limit of four grown bodies to a Bison(including the Air Bender steering, not a weight restriction, just a matter of space, you saw how crowded it started getting when Toph and Zuko joined in on the saddle orgy.(wrong choice of words not-withstanding, you know what I'm talking about.)