Realistic and beautiful live wallpaper of different cities with snowfall, moving clouds in different planes and colors that change dynamically during the day (full version).

Cities: Stockholm, New York, London, Toronto, Moscow, Paris, Prague, Seattle, Berlin, Kiev, Washington DC
Bonus: Seoraksan National Park, South Korea

If you're an advanced user you can also select your own image as the backdrop. In order to make it look good you will have to use a PNG file of a city/landscape with the sky cut out (transparent, alpha 0) and also the sides of the image has to be a power of two length (256, 512, 1024 etc). They don't have to be equal though. E.g. a png file with the dimensions 1024x512 will work fine.

Photo credits (flickr users)
Riddarholmen: gesternumdiesezeit
London: Karen Roe
Manhattan: Eva Abreu
Red Square & Saint Basil's Cathedral: Vyacheslav Argenberg
Seoraksan National Park: mendhak
Berlin: m.a.r.c.
Paris: Oh Paris
Seattle: Dave Morrow
Toronto: Blair Stirrett
Kiev: Andrew Bossi
Washington DC: Allie_Caulfield
Moon: Luis Argerich

OpenGL based.