I'm using Background Manager with great results, but for reasons unknown to me I am unable to add the same image to multiple Image Sets and unable to add existing images from the Media Library to an Image Set.
When I select the "Media Library" tab in the "Upload/Insert" browser only "Delete" appears for each entry, no "Add to Image Set" button at all. That only appears in my "Upload" tab after successful upload.
WordPress 3.3.1 with Background Manager and a Mailing List plugin. Please advise!