The standard advice for information display is to have no more than 5 to 7 or so items in any one group, so they are easily comprehensible. With such a large total number of categories, instant legibility is critical.

Rather than making each category name an image, you might do best to use the heading function to break the list down into related groups of categories, or otherwise provide "anchor points" at intervals in the list so the customer's eyes don't slide around so much but are able to focus on chunks of navigation information. The divider function may also be useful.

The range of products in your site is such that it may be a challenge to make rational groupings, but that's where I would start working.