Most guys lose some fat deposits, so bones tend to become more prominent. Also, losing some fat can make the facial muscles more prominent. The skin gets a bit coarser and can give an FTM face a slightly more rugged look. I've read that cartilage can thicken, but I don't know it that's true or (if it's true) how much. But that might slightly alter a nose, make it a little more masculine-looking. Anyone here know more about cartilage?
One of my most noticeable changes (apart from facial hair) is actually complexion. I'm ruddier than I used to be--I look much more like my father. The other change, of course, is hairline. That makes a big difference in my face.
I didn't get any chubbiness in the face when I started HRT, but I have some friends who went through that phase and now have more angular faces.