For me, storage.
What I would love is for a modular storage system - a system that can attach extra compartments on each side as suits the space, that have multiple compartments that can be combined to form larger sections in any direction.
So I guess a back board with pin holes where you pick a hole for the pin and each pin can be connected to the left./right/up/down to an adjacent pinto form a side of a box. Form any regular sized box and then into this box a drawer. So for instance a 1x1 square could hold a drawer of 2x2 plates, when it is too full, expand the hole and the drawer to 2x1 etc. Then when you have so many 2x2 plates so it is becoming hard to find break it down again so a 1x1 of red, a 1x1 of black, 1x1 of grey etc. I would cover walls in this. Over shelves, under tables, if there's a gap I could use it.