This suggestion is not about buttons and controls per se. I have a bit of a problem with the way the LR interface looks so dark compared and somewhat cluttered to other programs (such as Photoshop and Premiere Pro). I think it may be the very dark borders between and around panels. I'm guessingthe idea is probably to isolate the pictures, but for me it ends up providing too much ~contrast~ against the pictures.
I would be very happy if this became customizable or just les contrasty.