If the sellers have not left the property in the condition that was agreed....empty...then you may seek compensation for the cost to you. It will be a civil matter and probably won't be worth anyone taking action, so it will be down to how committed either party is to persue this matter. If they have left other items and the house in a poor state then ask them to collect all the items left and pay a sum for basic cleaning, this may settle the matter when they realise that it probably going to be more expensive than the item....unless it is a Van Gogh????