In addition to more variety (which I think will come as development moves forward) it would also be nice to see the clothing change with the quality. When you make "clothes" or "warm clothes" it would be nice to see that reflected in the character models.
Although graphics improvement is always nice, I think its best they focus on content atm. Don't get me wrong with this, i love this game, but what good is a new villager face, if after 15hours of playing you dont have anything more new to do?
Agree with the "more variety" thing, also when it comes to body types. I would also appreciate if the walking/standing posture of the female characters could be toned down somewhat -- they all look like they're in dire need of an orthopedist >.