Image Laws

Hello,
I have a question for you designers, how legal is it to alter a picture to fit your needs. It’s hard to put into words what im looking for, so here’s an example:

My clients wants me to take a picture of an ipod and then edit the ipod in photoshop, like change color, put an album picture in the screen… No logos will be visible.

I’m just not sure if this type of design is completely legal.

thanks for your help.