I think you might have a problem with explicitly referencing the mask as being like Dr. Doom. If you described it in a way that put the idea in people's head that it was a Dr. Doom mask, you'd be better of...that is assuming you still want to go ahead with that. The only issue i see is actually saying Dr. Doom
there is nothing wrong, or illegal, or actionable about merely saying a character is wearing a 'superman' costume or a 'spiderman' mask... or a 'dr. doom' one... or saying that someone is wearing 'harry potter' eyeglasses... it becomes a problem only if you make your character 'be' another author's copyrighted/trademarked character... and, as cog noted above, the 'fair use' exception does not apply in any way to what is being discussed here... before giving advice, or making pronouncements on legal issues with trademarks and copyrights, one should be well-acquainted with the rules and regs of same... it's easy enough to do by studying the ins/outs and cans/can'ts here: www.uspto.gov www.copyright.gov
A major factor is how the character or product is going to be used. A character wearing a Superman shirt might not be a big deal. But if the character wears the shirt while raping/murdering people, you run the risk of getting hit for trademark tarnishment. (The Superman logo and name are both trademarked). Even if you memorize the relevant laws (which would be difficult, because some states have their own intellectual property laws which must be followed in addition to the federal laws), a company with a team of lawyers can bury you in paperwork just because they can. They know that if you went to court, the law would be on your side. But they also know that you will run out of lawyer money long before Marvel will. Hiring a lawyer familiar with intellectual property law can help in a few ways. First, they can review your specific work against the law and determine if, in their opinion, your usage is acceptable. Second, they can give you a heads up if your perfectly legal usage may still draw a lawyer letter or two from the trademark or copyright holder. If they know Marvel cuts cease and desist letters for less than what you are doing, you should probably know that going in. I say all of this because we can argue all day. We can all quote laws and legal opinions. You can read as much copyright and trademark law as you want. Ultimately, if a big company wants to shut you down, their team of lawyers will get it done.
