besides the vast archive of pinterest theres movie stills [film-grab.com and others] i especially like using cinematography from 80s-90s horror/action movies n tv shows cus they fit stuff in the shot nice and obvious, old comics and illustrations spanning from the 30s to 90s (i have books of some!), at times i use myself + camera for very specific details if i cant find anything or cant see it in my head clearly.... for smut i like to look at scans of old porn mags and amateur stuff, or go down an internet rabbit hole lookin for stuff ... sketchfab.com is great for specific stuff sometimes too because you can move the models there too and many are free to use if its just reference! then also there's video games that can work very well for atmosphere/background references and such! taking a walk and taking pictures of things at times become very useful refferences too. basically, a lot of sources, but i hopefully i was detailed enough!