The Windows Mobile 6.5 interface looks a darned-sight better than previous versions of the operating system. If you're still not happy with it though, or you've got bored of looking at it then check out the Splendid Space Theme.
This elegant theme transforms the look of your Windows phone, adding a cool black background wallpaper with swooshy effects. The background also shows up on the Start menu and any text that appears in front of it is perfectly visible.
Splendid Space Theme is not particularly exciting and doesn't offer anything in the way of new menu icons. What's more, the URL of the theme's creator is constantly displayed in the corner of the screen.
However, if you're looking for a black skin for your Windows Mobile device then Splendid Space Theme is worth a look.