Found a great place to purchase some public domain images and am going to use some from Pixabay as references for hand painting. All will still be free to use both personally and commercially.
All uploaded backgrounds are free to use in anyway you want to without attribution. If it is a photo, it was taken by us then hand painted. If it is a background, it was rendered by us in one of our 3D programs then hand painted. You will never have to worry about where the stock comes from or if it is legitimate to use. Just enjoy and make beautiful artwork. Our only condition is that because the painting is based on our originals, you can't sell them as they are or offer them up to some stock photography place, you must make some sort of art piece with them.