I just finished new feature! Menu can now automatically select image for submenu items.
If feature is activated in backoffice, menu will choose one product (most valuable for now)
from category, or subcategories and display cart_default image (for now).
I have to reorder text and image also, for my own store.
This is how it looks:
Take a look at this commit: https://github.com/pauld-codes/blocktopmenu/commit/dab3820f2dc3f5db158b85ebeae59bb427a2262a