“It's up to you to tell the story.”
I was able to turn my age into advantage, and the contrast between my obviously teenage avatar and a convincing portfolio helped me distinguish myself from most other freelancers.
It was the same with my first job: I just approached a guy after he gave a lecture and asked him questions he found interesting. He was a CTO of an outsourcing company, and I asked if they were looking for C# programmers. I sent a very pompous resumé and got hired despite its silliness—it made them curious enough to land me an interview where I was able to show I'm a normal guy.
If you're seriously different from the rest, you can turn this into an advantage as long as you stress this point and make it an integral part of your story—not something you hide. People appreciate honesty and some humour too, and that's especially true in freelancing.
Exposing your vulnerability (yes I'm young, yes I'm a minority, etc) while showcasing your great work makes you look humane and more likely to be a great person to work with. You'll attract better customers—I experienced this myself. People you'll enjoy working for.
Your work speaks for yourself in either case, but in the end it's how you market your work that determines if the one evaluating you feels excitement (“This guy's so young but his work kicks ass, he must be a real prodigy”) or doubt (“This work is great but he's so young so we shouldn't hire him”).
Of course getting a lot of signed positive reviews is important, and pricing can be tricky too.