Reading the article of Tali in the wiki I found a picture of her without the mask.
Is it real or a good fake?
It appears that you need to have a romance with her to get the picture.
That picture of her is the actual picture used in-game. It's a gift to you from her after the Rannoch missions (assuming you're romancing her), and can be found next to your bed after speaking with her.
The image itself is a photoshopped copy of a photograph taken from a website that specializes in stock photos. (Stock Photo on Left)
Personally, I'm going to keep pretending that this fan art is the real Tali.