Copyright Aid

Hello. I'm new to this strange legal world myself ,so my comment may not be of any relevance at all, but I have just bought from a online trader 4 prints which were sold as vintage prints but are clearly not the original book plates or work they were taken from. The seller is selling multiple copies ...

I want to copy segments of wrapping paper which are printed with copies of paintings of long-deceased artists (Monet, Van Gogh, William Morris etc.).
Are images of famous paintings now considered to be "in the public domain" (not fully certain what this term means) and so I would not be infringing ...