There are guidelines: .png icons to ObjectDock, .ico icons to Misc Icons (Windows cannot use .png icons). Full icon packages should go to IconPackager. The idea behind the Misc Icons library was to accept icons which wouldn't fit into an IconPackage. Folks get confused though - if only I had a pound for every rejection which went out due to icons being submitted to the wrong section
I'd like to see a separate sub category in OD for backgrounds though, they are kinda difficult to find...
Spam in the library? I don't understand.
Yep.
I once suggested that we encourage people to upload sets, instead of single dock icon, but Frogboy pointed out that he, and others liked to search the library for specific, individual dock icons, and not for sets.