Long hair would rock!
If that is no option it could be richer animations and basic movements or the current highlights in their eyes per default and a super duper highlight as a trait as a sparkling highlight.
Perhaps default butterflies to chase and chasing bees and flowers or so as an extra trait.
Also extra pet options could count as a trait and perhaps for the kitties to finally wash that right ear for a change it starts to be smelly!
A trait could also be that they are twice as fast happy by cuddling for those who use no milk.
Extra room in their closet for clothes.
It could be a trait that it has became a royal cat which will more easily produce gems and other gifts to develop which gives access to new rare items.