If you can find 12v bulbs to fit, one thing you may need to look at is any switches. 110v switches are carrying very little current and the high voltage means that any resistance in the switch contacts won't stop the flow. However when you go to 12v, there are two changes:
- the amperage will be much higher (for the same wattage) and might be more than the switch can take - it may be OK, but it's not guaranteed;
- a bigger problem is that any resistance in the high voltage switch will lose you lots of voltage - the bulb may be fairly dim and the switch may get pretty hot.
110v and 12v switches are really different items - the design goal of the 110v switch is that it doesn't burn up when repeatedly switched whereas sparking is no problem to the 12v switch but that has to have 'wiping' switch contacts to keep the resistance down.
I suggest you rig one of these lamps to run on 12v in your garage and check that if you leave it on for an hour or two that the switch doesn't overheat, before you put it your tear.
If you've got no switches in the fittings, ignore all of this!
Andrew