If you want to get rid of excess postal art, you can donate your collection of postal art to the Museum of Moscow.
With my participation in the Museum of Moscow, an archive of postal art for art historians and historians is being created. Art objects will be used for exhibitions. There is one problem - transporting your gift. In some cases, a museum may pay postal expenses, but directorates are preliminarily needed:
1) Photos of your archive and
2) its short description.
If you are interested, write to me here, in the messenger.