The location where WB looks for skins is set by two registry keys. They must be set to the same directory.

HKEY_CURRENT_USER\Software\Stardock\WindowBlinds\wb5.ini\Installed\Path

and

HKEY_LOCAL_MACHINE\Software\Stardock\WindowBlinds\wb5.ini\Installed\Path

If you want to put your skins elsewhere then you can change those keys and copy ALL of the directories off the current WB skin directory to that directory.