Well, I just played through the part where the picture comes up and was pretty disappointed to find out the photo linked in this thread really is what is in game (though manipulated to have 3 fingers).
Sucks seeing that this is what they amounted to after 3 game installments for, but for me tali will always look like this in my mind:
I've never been a Tali fan or romancer, but I can sorta understand the agitation with this "reveal". At the very least, I figured they would have done a graphical design of a person's likeness, similar to the photo link in the post above. But from a financial/time standpoint, this is the most efficient way to go. I mean, to satisfy the dudes that would romance Tali, a good-looking real-life Tali model could be 30 grand for a day, just to take photos and who knows how much if you wanted to go the fully CG rendered route. But for a couple hundred bucks, you can get a photo, draw some implant circuits on it, clean up the fingernails and boop, Taaahhhh-leee!
Is it lazy? Of course. Is it done because other things needed to be implemented? Yes and in the end, I'm glad they had more time to design a weapon modification bench instead of drawing Tali's face.
During the scene at Rannoch, it was clear when Tali removed her mask, at the time of making that scene, they were still debating on showing it.
It was also very clear that Bioware themselves were indecisive about the issue. The fanbase was clearly split right down the middle, even the Tali lovers were split.
What was the best course of action? Leave the reveal as a choice in complete control of the player.
Granted, they clearly could have done a much better job with the photo. Finishing the Rannoch scene would have forced the reveal on the fans that would have preferred to keep her a mystery. Not revealing it at all would have upset those who did want to see it. Leaving it as a choice, by allowing players who did want to see her face to find the picture makes the most sense.
In the end, we now know what Tali looks like, it's just up to fanart to make better work for those that want it. Bioware has closed the issue. Disappointing in a way, but there's nothing we can do about it at this point. Maybe in some DLC we can get a new outfit for Tali that has a transparent mask, but even then the fans will still be upset about it.