Well, you have the perfect ingredients for a sort of shepherd's pie! Mix the chopped ham with your vegs and some sort of gravy, like a can of cream of celery soup, maybe, or cheddar cheese soup. You didn't say what kind of potatoes you have, but you can make mashed potatoes out of just about any kind of leftover potatoes. Spread the mashed over everything and heat in the oven till hot all the way through.
Or you can make a ham, veg and potato pot pie. Similar, but with a pie crust.
It's worth checking out the thread Alix posted above, too. LOVE the last line of Aunt Dot's post there: "I think it was Dorothy Parker who said 'Infinity is a ham and two people'." LOL! Dorothy was the best!
Lee