Hmm... my thoughts?
- Definitely function over form. It would be about a practical use, not an iconic design.
- This tells me your going to see a lot of form fitting body suits, with zippered boots/shoes.
- Heroes without invulnerability are likely going to incorporate body armor in some way, but you want to stay away from bulky pads and rigid plates unless your going for a military/knight look. Think flexible, like this.
- You will ether have to go fully masked or be willing to give up your secret identity and go maskless. There is simply too many cameras and facial recognition software is pretty good now. If you can't conceal your face fully, don't bother, because someone will find you.
- On that note, the best way to conceal your identity is probably something like a motorcycle helmet or something similar. It's practical, easy to modify, easy to acquire, and it completely obscures the shape of your head. Another option would be something like a ballistic mask, which does the same job and is bulletproof.
- Gloves are going to be necessary to protect your identity. Get something with material on the fingers that will let you use touchscreens like on an iPhone.
- Utility Belt is a must. Your going to need space for zipcuffs, lockpicks, a camera, etc. Don't try to carry a cellphone unless it's a cheap disposable one.
- Capes are out, backpacks are in. Single strap, tightly wrapped messenger packs are light weight and don't get in the way, yet provide more space for gear. Think Faith from Mirror's Edge or Cole from Infamous. Great for stowing your grappling gun or files from a corrupt banker.
Cosmetically, it really doesn't matter. You can go with whatever color you like but dark greys with a splitter pattern would be the most practical for stealth in an urban area. I suspect you'd be seeing a lot of two-tone looks though, because they carry the modern style sensibility: minimalist, yet eye catching. Probably glossy finish to the suit unless it's stealth wear, in which case it will be matte.