Making a list of additional resources for all your #OSRJuneJam needs! Will update as I think of more. Here's some starters:

https://www.flickr.com/photos/129824703@N04/albums/72157671625640022 - art!

https://www.oldbookillustrations.com/ - more art!

https://karenswhimsy.com/public_domain_images/ - more art!

https://publicdomainreview.org/ - still more art!

https://www.flickr.com/photos/192445357@N05/galleries - you guessed it!

https://greygnome.com/free-art-assets/ - even more art!