Personally I would like to see the ability to put text behind layers (it is always on top now, regardless of how you order it). It would be nice if it was more dynamic. I would also like to see more flexibility with default graphics when switching emulators or game lists. Finally being able to manipulate the top and bottom lists more would be awesome (individual like control, transparency, fades, gradients, strokes, etc).
Otherwise it is pretty solid, just not very dynamic. Frankly though as much as I would like to see these changes made, I would like a general update a lot more (64 bit support, .154 ini support in gui mame control panel, a better gamelist system, and better performance overall)