Can envelopes be said to be publicity materials?

Envelopes are publicity materials, including three types: first, printed materials, including internal publications, books, picture albums, newspapers, yearbooks, official documents, envelopes, notes and so on. Second, advertisements, including slogans, display boards, colorful flags, posters, notices, notices, revelations, banners, billboards, leaflets, ink painting, etc. The third is souvenirs ... in which envelopes are included in promotional materials.