Flickr.
Look for the pics that have the (CC) logo on the page. It means they're for creative commons use so long as you credit the original photographer... Said credit can be <!-- commented out --> in the HTML too, and it'll still be legal usage.
Celeb pics are only legally problematic if you're implying that the celebrity is endorsing the product, or that any text on the site is their words. You'll run into C&Ds or a straight out suit for that.
You may run into issues of the IP owner DMCAing you for the pic too.