Inserting content between rows of new products

Is there any way to insert banners or other code based content in between rows of new products or other areas such as featured products? So if you have it set to 20 new products with 5 rows of 4 columns and want to stick an image based banner between row 2 and 3.

Not in stock Zen Cart, nor in any existing plugins that I know of. However, it would be possible to adapt Listing Subheadings from Plugins to work on these types of listings. It would require applying the mod coding to the new listing files, similar to the way the Flexible Product Listing files are tweaked to work with LS.
You could already use Listing Subheadings to put your banners in category or product listing pages.

This idea is for the front page. I guess another more annoying way to do this would be to have new products limited to a certain age of inventory, put a banner below it, then have featured products below that and make sure any of the featured products are older than the limited new products' age.

I wish there was a way to hack the module code similar to hacking wordpress to have a banner between posts on the front page of a blog (not that I'm comparing the two, just using WP as an example of what I'm seeking to accomplish).

I wish there was a way to hack the module code There is, it is included in the Listing Subheadings plugin files...