Themes based GUI for OPENGL ?

I am making this game like Age of Empires…i was wondering if there is a GUI library available which supports themes…cause i want the buttons and screens to look like Age of empires not like windows.

I have the reqd textures and stuff and i wan the gui to use THEM instead of its default. Something like PICOGUI for SDL.

And by the way in such a GUI would it be possible to show the game map in the center with button below in a slab and stuff?

Check the GLGooey library, it has skins and virtual function draw() for widgets.