A superhero uniform has only a minimum of necessary features. Gloves and boots are always a good idea for those whose skin is not made of stone or steel. Capes are optional; not everyone can carry them off. Certain nocturnal avengers may favor utility belts and pouches, while those with metahuman powers would find them superfluous.
The only absolute necessity, the one thing a hero or heroine cannot do without, is an insignia. Their logo. Preferably prominently displayed. After all, what's a hero without marketing?
It's fascinating to watch the evolution of the superhero costume over the decades. The dudes' costumes have become less colorful and more practical with body armor, a plethora of pockets and pouches, and most happily, less spandex. The girls' uniforms... well, they didn't exactly toss on a pair of overalls to tussle back in the 30's. These days, it's gotta be a challenge for the artists to pinpoint which scrap of cloth they can erase without the whole thing disintegrating into separate atoms.
Below you can see a couple pose studies. I was trying to push the poses to the extreme, until I realized that since these are superheroes they're already there. Visually, I had a great time playing around with the shapes and patterns throughout the piece, not to mention the positive and negative spaces. The chiyogami papers in the cape and uniform are particularly beautiful with hints of gold and glistening white.