I’d like to see a way to roll up sleeves on clothing, and to wear bandanas around your head and things like that, as well as personalising clothing (this could be done by getting achievements, so if you do a certain thing and get an achievement, you could have an ace of spades in your helmet or something like that) this could also be a better alternative to skins and cosmetics.
Rolling sleeves up and things like that could be done by right-clicking on the item and going to the description window, and having a little arrow selector in the bottom corner or something like that.