Unless the photographer is in a "work for hire" situation they own the copyright to the images made. The photographer working for the local sears portrait studio is in a work for hire situation, and sears portrait studio (actually CPI Corp) owns the rights to the image. You purchase limited rights from the photographer, $40 for an 11x14 , $500 to use on a billboard, $2000 for a million print magazine run etc. But he owns the image. You cannot copy the print you bought and therefore duplicate the image without purchasing the rights to do so. Yes you can copy it but we're talking legally here.
As the owner of the image the photographer, with really no permission needed can use the image that he owns the rights to to promote his business as he sees fit. If that means that usage in his studio for samples hanging on the wall or in a sample book, he has the rights to do so. He cant sell prints as that invades your privacy, but usage on a website slideshow is also a premitted use.
He further solifidied this usage in the contract you likely signed when you bought his services, but even without the wording in the contract, he can use it for self promotion.
Now any photographer I know usually goes out of the way to inform the subject that he wishes to use said images for promotion and with rare exception gets the permission for the cost of the $40.00 11x14 (his cost $4) or some similar low cost trade.
In the scope of copyright, this same thing applies to every one of your designs that you make. They are yours, you are the artist, you posess the copyright. Most may be derivative works featuring an image, a graphic, and a font or element of type but its your work and your copyright. When a customer takes your design and has another shop print it as is, you have been stolen from.
