Don't know if you're aware of it, but the Russians/Soviets had some of the cheesiest, campiest sci fi art on hundreds of thousands of sci fi pulp fiction novels from the 1940s through the 1980s.
When searching, try "vintage USSR sci fi art" and similar to see what turns up. I lived in East Europe for a decade. Even as late as 2005 or so the book stands were crammed with the stuff. I love it and just wish I could read Russian enough to have collected some of them.
Great thread, OP. Thank you!