I'm not very good with mugs, but I think it looks pretty good, the armour's neat. The main issue I have with it is that his head is just too big for the body. Compare it to some of the actual FE portraits:
If the tops of their heads align, his chin is in line with their shoulders. His mouth is in line with their chins. Not only does that mean he sticks out from the other FE mugs, but it makes his body look small in comparison. You can tell both Dorcas and Hawkeye are big, beefy guys, but the size of Zelgius' head makes his body look kind of scrawny. So I recommend shrinking the head, and then moving him up in the box so you can show more of the armour.
Something like this!
Edit: Looking at it again, I've made his neck look really long. Maybe try lowering the head and pulling the shoulders up?
(Probably not this much though.)