SPOILER WARNING! Considering how there is only one point in time where Tali ever took her mask off while off a ship and while the sun was setting, this is pretty much the only scenario that makes sense for her picture.
As for her revealed design, I actually really like it! What I do NOT like is how it was revealed through a clumsily photoshopped stock photo. They couldn’t have just copied the basic Tali mesh, make a face out of various tweaked FemShep facial assets and then put it in the scene spoofed above, where she takes her mask off anyway but the game doesn’t show you? Just sayin’.