That practice is similar to adding a "powered by X Company" link. The fact that it is an image doesn't really change anything. Clicky.com also uses this method

That practice is similar to adding a "powered by X Company" link. The fact that it is an image doesn't really change anything. Clicky.com also uses this method. I do not think those links would be penalized with Penguin for the same reasons I previously mentioned. Is it a cheesy way to get links? Probably. But you should be fine.