Robin?

Flash or Red Tornado?

Impulse?

On second thought, I think flash. This red looks a bit too saturated for Impulse's costume.

Super-Man

I'm going to throw it out there for everyone to consider that we might not be looking at a red suit on a white background. I think we're looking at a red jacket and a white shirt.

Bulleteer?

^^ true. You can see a bit of the collar on the top right.

Darn I was thinking Bloodwynd or Powergirl.

Superman’s “S”?

It's been 2 days now, tell us who it is!