I use isometric tiles for everything in my game.
I model the object in blender and render it using an isometric camera, then use Gile to give the tile a transparent background.
Depending on the size of the object, it may be 64x32 or 64x64. (I use a sizing algorithm to draw the tile in the right spot when I draw the map)
The object is placed on a layer with a higher zorder or depth than the table.
0 = ashpalt/concrete
1 = dirt
2 = grass/ floor
3 = objects (collidable, walls, trees, signs, furniture)
4 = decorations (paintings, candles, plates)
5 = collide layer (for detecting collisions)
I haven't created any objects that are wider than 64, but using the same drawing algo based on size should work with those too.
Heres a pic...