Look at how the 'Beer Keg' item spell works since that changes your cursor to the keg you are about to place. I know it is possible to do but I can't remember if you need client side edits (spell DBC) for each object you want to change your cursor to.
edit:
Just looked it up, triggers spell:
Brewfest Pony Keg - Spell - World of Warcraft
Which has spell visual ID: 353
Spell Effect 1: TRANS_DOOR
Spell Effect 1: SUMMON_OBJECT
Misc Value A: 186738
SpellVisual.dbc: 353 points to spell kit 380 and 1165
SpellVisualKit.dbc: 380 points to 7518, 1165 points to 142
SpellVisualEffectName.dbc: Neither of these ID's exist appropriately.
TL;DR: I confused myself looking it up and I have no idea.