Well I figure it like this. If he created them then he owns full rights to the logos and full rights to display them... the only way I'd see him not being able to is under 2 conditions:
1. He gave up full rights to the website owner of the logo/template (assuming it is a web design business he does)
2. Or if the images and graphics are copywritten (I'm once again assuming a web design business)
Any other topic of clients, I don't see why he couldn't... I mean after all they should think of it as a blessing for more traffic
