Have you heard about a huge collection of PBR textures by StruffelProductions? A project called CC0 Textures features more than 100 textures. The best thing is that you can download everything for free, with no need to register. Some of the goodies are event presented in 8K resolution, which will be perfect for different close-ups. Some of them present a 4K “alternative” which is quite adequate too. What about the licenses? All of the files have a creative commons zero licenses, so you are free to do whatever you want with them.
Physically based rendering allows for incredibly realistic surfaces, but generating good a good PBR texture ain’t easy: You need to wait for good lighting conditions, go outside and shoot the textures, stitch the images together to get one high-res image, make that seamless and then generate all the maps. This process does not only require equipment and software that not everyone has, it can also take quite a while.
That’s why most people usually rely on sites like Textures.com or Poliigon.com to get all the surfaces they need. And that works great if you are willing to spend some money or live with the free low-res versions on Textures.com. It does not work, however, if you wish to distribute your work in any other way than just a render! Reselling textures from Poliigon or Textures.com on sites such as the Blender Market is a slippery slope, to say the least.
That’s why this site exists, all textures and maps on here are licensed under the Creative Commons CC0 License, which allows you to do pretty much whatever you like with these images. Use them in your renders (even commercially!) or bundle them with your models! And you are not even required to give credit for them (although I would, of course, appreciate that…). If you have ever heard of HDRI Haven – It’s basically that, but for PBR textures!
You can learn more about the project and get the textures here.