petz > paintings
Some paintings you can put into your game, just put them in your Paintings folder and right-click a photo frame to select the BMP.
horror/thriller posters
Cropped thriller/horror movies, both new and old. The Weapons and Jaws ones fit shockingly well for the ratio needed.
dfw booklet covers
content warning: imagery of drugs, needles, and alcohol
These images are sourced from DrugFreeWorld.org, a wonderful resource on drug education, these being the covers for the various booklets. I found the style to be very interesting and fit a good shape for paintings.