Navigation teasers - how to do in backend?

Hi! I need to make a dropdown navigation, where for every parent navigation item, in the dropdown area I show the child pages + 3 images with a title linked to other pages.
I would need something like the 'Custom Navigation' module with an option to select images (or add a custom class, and get the image from the page), the problem is there I can not define levels.
Is there an extension which could I use for this? If not, would be easier/faster to change/extend a core module, or should I create a new one?
Thanks!