adding visual categories on pages

That sort of presentation is typically provided by your theme. There might be a plugin that does something like that with any theme, I’m not sure.

If you want to custom code something yourself, that’s feasible. Getting a list of categories can be done with get_categories(), but unless you already have code to associate an image with each category term, you’d need to develop something. Or come up with some other way for code to get a usable image, such as the featured image of the first post found in that category.

With a list of categories and associated images, it’s a matter of looping through the list and outputting img and a tags for each. To get the link text to overlay the image is a matter of the right CSS, as well as for getting each image into a grid layout.