Legal Question in Business Law in California

That depends. You can if the original photo is in the public domain. You would otherwise need permission from the copyright holder. You might need permission from other people as well, depending on who or what is in the photo and on where it came from. Your modifications could also raise legal issues.

You may want to consult with a lawyer before you get started. Avoiding problems is often much easier and less expensive than solving them after they arise.

Good luck.