While I agree linking to your client on your website doesn’t put you in the wrong, linking to their site with a picture of their layout on a web design company’s page does make it seem like you designed it.
Even though keith may have used a template, you still didn’t design the layout either. If you are going to link to their site using an image of their layout, you definitely need to have a note saying you didn’t design it. Especially if you are a web design company, as that is VERY misleading. Did you do the designs of any of the other websites in the Client section on your website?