They showed a screenshot of being able to select wallpapers from "available" wallpapers. I'm hoping available in this case means whatever wallpapers you have applied to your house currently and whatever wallpapers you have in your inventory.

If SE is being kind it will copy the wallpaper from inventory instead of consuming it and the note about it being lost on removal is to stop people from creating endless duplicates. But what I fear is that it will only be from wallpapers in inventory and consume them which means 1 per partition...