There's been a lot of jokey articles about what Bane would look like with his mask off. But seriously: what would Bane look like with his mask off? Courtesy of some behind-the-scenes photos from the 'Dark Knight Rises' set, we have a little bit of an idea.
Though there is a quick moment in the film where we see Bane without his mask on, it's before he had the mask at all, so it doesn't give us any insight as to what's doing under the mask.
Tom Hardy didn't spend a lot of time in character out of the mask but here are a few shots of him maskless from the 'Dark Knight Rises' set:
Well, he looks kinda like Tom Hardy...with a really weird suntan. you can also get a closer look at Bane's scar on the back on Hardy's neck. It's never fully explained why he's got the scarring but the mask is used to deliver a constant anesthetic keeping him alive. You also get a sense of how big Tom Hardy got for the role - and we don't mean just muscular.
It's interesting that Christopher Nolan chose to elaborate a bit on the Bane backstory when the Joker's story was kept such a mystery in 'The Dark Knight.' We may never know how mangled Bane's face really was underneath the mask but maybe that would explain why he talks like that.