You need to put them on a higher layer and then make then make the tile solid where they would be on layer 1. It's best to have display all layers, if you're doing this.
Another thing you can do, is get your floor tile and then go to Image, then Layer Tile (or just press Ctrl+L) then a window will open up that has a button that says Open Tile, press it and then go to the tile with your chair/decoration/shelf and then hit OK. Make sure you Save Tile As, so you don't save over your floor tile.
The first way I told you, might work better if you don't want to create a new tile for every different floor type.