Salvador Dali is one of my favorite artists of all time so I was particularly taken with this theme inspired by the work of the wacky painter.
Surreal Piano III features a background painting of lots of surrealist-style piano keyboards floating around in a spiral. It's definitely very eye-catching and is one of the most original Windows Mobile wallpapers I've seen in a while.
Aside from this striking background image, Surreal Piano II adds very little else to your interface, other than a transparent Start menu bar.
That said, Surreal Piano III will turn your Pocket PC into an interesting talking point.