If you're going to put it on casters ... please make sure that you use the locking casters when ironing.
Otherwise, it'd be too easy for all to start moving ... and you could easily get burned.
I put a rectangular piece of plywood on top of an old metal ironing board and have been quite happy.
Being that I never take my ironing board down, I have been starting to think of topping a chest/cabinet etc. to create storage in the space under the ironing board.