Okay, it's certainly not an eight-heads-high heroic figure, but enough to not embarrass myself in costume -- if I eschew the lean-mean or hypertrophic characters and go for someone stockier. In my younger days I could go for a pre-blue-fur Beast, or maybe a Kirby-stye Thing if I could figure out how to do the rocks.
Okay, but all right, Mr. Demille, I'm ready for my close-up:
Here's where it gets dicier. I usually wear glasses, but I can lose them for the costume, since I only need them to, like, see and stuff. I keep my head shaved; I could grow back a tonsure or Picard-fringe, but at this point, that's all you're going to get. And I wear a doorknocker beard that I probably wouldn't shave for casual cosplay.
So, within those restrictions, what are my best character choices for a costume? I mean it's not just the bald part - that's a fairly low bar, what with Lex Luthor and J'onn J'onzz and so on. It's the bald and bearded requirement that gives us trouble.

Perhaps more widely known is Ming the Merciless from Flash Gordon. With a little Grecian Formula and perhaps some wax, we could be good to go with this. But I really want to go heroic, not villainous, and I'd like to avoid the whole racial stereotyping issue as well (although I guess later incarnations of Ming made him a lot less "Asiatic" and more generically alien). And if possible, I'd like to go with a comic book character.
My recent choice for profile pictures and avatars and such has been Vulko, the science adviser/prime minister/whatever to Aquaman and/or Atlantis (depending on which version of continuity currently holds sway in the DC multiverse). Once again, I think the resemblance is there; but Vulko is really not recognizable to anyone. Although cosplaying the sidekick to a superhero whose name has become the very definition of lame might be the height of po-mo irony, I'm not sure explaining that over and over would be much fun.
All right, here's a bona fide hero: Green Arrow. Specifically, the old Green Arrow from The Dark Knight Returns. The character is popular enough, even getting his own TV show now. Of course, DKR Oliver Queen just looks like an old one-armed hippie carrying a bow and arrow, and only the hardest-core comics fans will even get it.
Okay, let's quit fooling around: right now, the biggest name in the superhero arena with the general public is, of course, The Avengers. That's where we have to go: if you pick an Avenger, you can't go wrong, right? Now, if only there was a stocky, balding, bearded Avenger...
Oh, wait - there is! Doctor Druid!



I'm sorry, where was I? Oh yes - my costume. Dr. Druid FTW!
Of course, I'll still have to explain myself to everyone.