My Windows 7 32-bit Professional only allows solid colors on the desktop wallpaper. Any image selected won't be applied.
I've already tried the process described in the other SuperUser question (uncheck Remove Background Images on Ease of Access Center).
I've tried using REG ADD "HKCU\Control Panel\Desktop" /v WallPaper /t REG_SZ /d "path_of_image.jpg" /f and it didn't work.
Also, I've read that Remote Access software can cause issues with the desktop wallpaper, but I haven't checked if that's the problem.
Another strange thing I noticed is that whenever I try to change the image, an "a.jpg" appears as selected. I've found that file at C:\ and it contains the Harmony default wallpaper. Is it possible that a script or software is setting the wallpaper to that file? Is it safe to delete it?