Hi there, and welcome!
There isn’t a dedicated design team, unfortunately, but I’d personally think any project would greatly benefit from one. Sadly, as it is so often the case, even awesome proposals don’t get implemented if there is nobody to implement, so it’s a bit difficult to have a dedicated design team.
There are talks (for example in What if.. diaspora restarts without the handlebar and backbone) to completely rebuild the entire UI from the ground up, instead of trying to fix/improve the current frontend. This would be a great opportunity to re-think UI and UX from the ground up as well.
If you have any specific ideas or suggestion, feel empowered to just raise them here on Discourse (the #features-and-ideas section sounds perfect for that). I have to be honest and say that it’s probably unlikely that there will be any change short-term, but I see no reason why that needs to be true long-term, especially if the whole frontend is rebuilt anyway. 