You better spend a few hours reading the archives here......This subject has been covered "extensively" in the past...
All images are protected under "copyright." So any use of an image without license or permission could get you sued for copyright infringement.Do I need to have permission to use any image, no matter the source?
The exception are images that have been released to the public domain. You can specifically search for public domain images. But keep in mind, this only satisfies the copyright issue. You need to consider trademark and right of publicity laws as well. If the content of the image contains a trademark or person's likeness, you need additional license or permission.Or does it depend?
No, just because you alter someone's work doesn't negate their ownership or protection of the original work.Does the rights usage change if it has been altered?