I thought it was a bit too good to be true that such seemingly high quality art was put up for free, and so many of them for that matter
After a careful look at some of them, I can pretty safely say that this was likely made with AI (Creator, if I'm wrong about this hunch, please provide some of the process as proof). A lot of these images have the hallmark of AI's bad, messed up hands.
I personally would not be using this for my projects. But if other people want to, I encourage you to take a good look at the images and decide for yourself if you want to use them or not.