Did you know that the Metropolitan Museum has a huge online collection of art that's in the public domain, that you can browse through and download high res versions of?
Here are some examples of the things you can find there!
https://www.metmuseum.org/art/collection/search#!?searchField=All&showOnly=openAccess&sortBy=Relevance&offset=0&pageSize=0
@soaku Yeah, it's great!