T.G.I.Beta
(1)
KhakiXP_small and (2)
KhakiXP_small_menu
These two skins are both optimized for use with 7.5 and are designed for use with small buttons in all instances. The only difference between them is the image used for the top toolbars. If you run a visible menu bar, choose number (2), if you do not, choose number (1). Much of the design for these skins came from the excellent SlateXP skins by
Marc Foumberg.
(3)
KhakiXP_Simplified_Native Skin 
The Native version of the KhakiXP skin is based heavily on
nontroppo's open source
Breeze skins. It is designed to use less resources than the normal skins while retaining the custom buttons.