I had fun squashing a few undead who were nomming on a corpse underneath a chandelier - which I dropped on their heads. I died soon after though, and playing through again, is it possible to lure more under there (there's a load hiding right behind it)? If so, how?
Run up to a larger group
Make a funny face
Retreat to the chandelier
Better yet, grab a friend with a tanking-type monk or barb, let THEM go make the funny face, run the group back to the chandelier and park themselves beneath it, then as the mobs all crowd around hit the switch.
I guess the simplest of answers would be to find another nearby pack of monsters, aggro them with an attack, and lead them in the direction of the chandelier you wish to use.
Is there something more specific you are looking for?
I frequently use the collapsable walls for large packs of mobs by leading them in that direction and hitting it when it will get the maximum number of monsters.