Many sellers don't mind if you use their pictures, but you should be aware that many sellers put an effort into taking the photos (adjusting the quality, removing reflections from the jewel case etc), especially if they arrange their photos in a special way, so that the picture itself is like their trademark. Why do you think many sellers on ebay photoshop their names somewhere onto the pictures? Other sellers may place the CD on a paper sheet with their names on it. Why do you think rapbay has that "rapbay"tag on every CD in their store? Hell, some have even included a small message on the photo, something like "take your own pictures".
Of course, most sellers won't mind or won't even know, but in respect to the one that has actually taken and prepared the photo you should at least have in mind that if there is a name on it, maybe the seller has put it there for a reason. Especially if you plan on putting up auctions on ebay.
but I guess you don't give a fuck anyway.