Nope, not at the minute, but feel free to make suggestions. Remember though that any changes should not bloat or slow things down.
Well, this is not really a skin feature, but what about adding an option to toggle to Main mode when hovering one's mouse over the Mini mode? Feasible? Enjoyable? This way I could hack myself a little better UI behaviour (hide controls for mini mode/add easily usable controls without increasing Mini mode size which would in turn cover important Windows UI elements).
I still want those fillable slider thingies I've been nagging about for years though! That could make some skin authors make skins that stand out a little bit from the crowd.
I've shown this before, but it's kind of my "dream" to one day be able to make something along these lines:
And again, for the umpteenth time, separation of font/colour settings of all playlist items. Crappy, tiny, old mockup here of what it could do (minus the periods, but such a feature could be nice as well, but I'd wager I'm alone in wanting something like that):
Much much easier to quickly find the info you're looking for, since you can "tune out" certain elements of different shades (like those, IMO, mostly useless playlist numbers).
I'm in the process of making a new miniskin for myself, since I'm now at a higher resolution and my old miniskinses (and these mockups) don't lend themselves well to 1600x1200 @ 19" (CRT), but all the limitations are pretty frustrating, to be honest.