SJN: You should be able to pick the background image by selecting from the drop down box with a dotted rectangle around it. By default it has Skin default written in it, but clicking on it should show you 29 other options.
All I see is a white square (dropped down default) and nothing else. No options whatsoever.
Here's my info:
WindowBlinds version : WindowBlinds 6.1 (build 49 x86)
WindowBlinds is installed correctly on this PC
WindowBlinds appears to be activated on this PC
Your machine supports per pixel borders on WindowBlinds skins.
(Plug and Play Monitor) 1 is attached to NVIDIA GeForce 7800 GTX
Wblind.dll 2008/02/19 17:51:20
Wbsrv.dll 2008/02/13 16:15:10
Wbconfig.exe 2008/02/20 13:52:33
Wbload.exe 2008/02/14 11:05:14
Wbhelp.dll 2007/08/27 11:54:07
Wbui.dll 2007/12/01 16:43:05
Tray.dll 2007/09/12 17:58:21
Screen.exe 2008/01/11 12:14:18