Hello!

I'm planning to purchase some photos that I will be using as assets for my side-scroller project. The photos will be used as background art in my levels, and I will be modifying the images heavily in order to make them fit to the overall artistic style and to give them a uniform feel. I'm first and foremost a hobbyist, but keeping the commercial door open too. So the license would have to allow commercial use as well.

However, I don't understand a thing about photo licenses, and the guides make me even more confused... Can someone help me and explain which licenses would be safe here? I'd need complete freedom to modify the image and to use it in a commercial game project.

Thank you!