What should you need to change in Bitcoin client??? You need to bloat the GUI with skinnable themes to attract additional bunch of retarded users who judge software purely from so called "eye candy"? (search youtube for "happy tree friends eye candy") (lol)
No. There's a big difference between stupid skinned themes designed by programmers and a clean fluid looking interface that looks contemporary and is designed by a designer.
Everyone, please don't take my original advice. From the replies here, it's obvious it would be confused with some programmer's idea of what a cool skinned theme would look like, which is just wrong. Stick to what you're doing. Maybe someday, you can hire a designer and make it look really good.