No, wall lamps that come with houses cannot be removed or replaced with something else on top of it (for example, store or any item). However, if you purchase extra wall lamps from the Tibia coin store, furniture store or hireling for example you can remove or add these ones as you please. Sometimes previous owners leave their extra wall lamps if they transfer you the house. Make sure you try to drag the wall lamp off to see if it comes with the house or not.