Image only on main page and category pages

Hi,
I have nearly completed my site thanks to these help forums, but I have a question I can't seem to find an answer to. I would like for my index page to look like this page:

https://www.caydesign.com

Also, on that same site, when you click on view by artist or view by subject, that set of images stays in place, but the categories expand only in the menu on the left side. I'd like to do this in zencart.

I can't seem to find any instructions on making a montage of images for the main page, and the category page. Can anyone tell me how to accomplish this?

Here's the site I've built in zen-cart:

https://www.caydesign.com/zencart

Thanks in advance,
Melissa

when you click on view by artist or view by subject, that set of images stays in place, but the categories expand only in the menu on the left side. I'd like to do this in zencart.
You can create these categories and link products to/from them to other categories