This one is just in time for Halloween here in the US on 31 October.  This new theme from the Windows 7 Personalization Gallery will bring some spooky backgrounds and sound effects to your Windows 7 computer.

Horse on Cobbled Street, Prague, Czech Republic Profile of a Crow Full moon covered by a layer of clouds, 31 Oct 2009, Portugal
Fruit Bat Hanging from Branch Mysterious Forest in the Pacific Northwest Pumpkins
Owl with Yellow Eyes Bare Trees at Night, Venice, Italy Mysterious Gate with Textured Wall, and Two Bats in Flight
Gargoyle on Building at Night Charles Bridge crossing the Vltava river in Prague, Czech Republic Fog in Copou Park, Iasi, Romania
Harvest Moon through Clouds, October 6, 2006, Canada A Jack-o-Lantern in a Pumpkin Patch, Canada Branches Surrounding Harvest Moon

Download the Eerie Autumn Windows 7 Theme