WB4 is awesome. You guys did a great job getting everything skinned.
If it's possible, make the user name text position fixed so on a domain without a user icon it still aligns from the same laft margin.
Make the mouse-over text color seting work for menu backgrounds on the programs list and 'special' menus where there are icons in the list.
Bring back the explorer backgrounds and give more color options for transparent explorer backgrounds (like shades of grey).
Allow animated button mouse-overs for titlebar buttons.
Tile the shell styles background image.
Titlebar text effects like shadows on UIS1.
Activate the mouse-overs on scrollbar thumbs (which it does do in the shell styles area).
Mouse-overs on scrollbar arrows and maybe add one for the corner re-size grabber thingy in the arrows images.
tell us what "glyphs" are...
Document all the standard or recommended sizes for windows elements.
Increase the number of buttons possible with plugins and Shift/Ctrl functions in a skin. (30 is not nearly enough

)