It depends on the content of the hub!
If it's a photography, art or craft hub, then I think photos or scans are as important as the words that describe them.
Also, how-to instructional hubs can have more photos to illustrate the instructions - I know many people who hate cookbooks that don't have photos for every couple of steps.
For stories, academic articles, etc. then I think the number of photos can (should) be fewer, and should be topical - used to add extra information or clarity to the written information (and not only for decoration). Having said that, a 'decorative' photo, well chosen, can pull more readers to a hub.