Where can I find royalty-free and high quality public domain stock images? I would like to use them to make videos. I need a good resource of stills to draw on that won't cost anything further than an initial fee or nothing at all. Alternatively photos that are restriction-free would work.

Most of the sites I have found so far aren't as good as I would like. I prefer graphics to photos and want to use more model-free images than not. That way I don't need to wait around while I obtain a model's permission for use.

Any suggestions would be appreciated. Thanks!