Make a biodome habitat module. Basically, something with windows on the outside and plants on the inside, that can store kerbals for moon and space bases, or long-range (interplanetary?) spacecraft. I can't think of what sort of resource it would produce or store, if any, but it would look cool if created by a skilled artisan It sure beats hitchhiker storage containers! Also, if you want to go so far as make an IVA for it, you could add some fun stuff like items hidden behind plants, that only a Kerbal in a particular place can see, etc. You know, easter eggs. Maybe even AN easter egg! Oh man, I'm liking this part already!