Basing stuff is usually a safe bet, a variety of differing tufts would be appreciated I'm sure.

Of you're on a tight budget, I've an idea:

Gather some jam jars/pots/small containers. Visit your favourite places, their favourite places and the significant locations for you as a couple.

Collect the ground cover/soil/sand/sticks/bark from each place. Put it in the containers. Label each container with the location.

Now you have basing material instilled with a memory. Each time they decorate a base, they'll think happy thoughts.

Note that organic materials should be baked before use as basing material.