Why not leave a note for the new occupants? Share a few cherished memories and wish them as much happiness and joy in the home as you had. If they are going to be moving in soon, leave some fresh wildflowers on the counter, or fruit from the backyard tree.

I think most people, under the stress of moving, would be delighted to find such a thoughtful gesture. And it might give the old house a leg up in the happy occupant department :)