Yup, we have at least 100 pages on our site which are linked only by images, and all have PR and some rank well too! Most are "click here for the larger image" type, and the large image is made into a proper html page. A waste if the link just goes to a jpg.
Just one tip. Alt tags in image links will also help towards the keywords of the linked page. It is similar to anchor text but isn't as strong of a boost.
