Possible other than yes/no?

I'm reaching a bit here, but I find myself in need of (well, more wishing for) a yes/no-type column, using three values, that uses choices other than yes/no (and empty). Is there a way to do this that I've missed?

I would even settle for changing the images, and adding one for the blank value. I also would prefer the same means of filling it — or even better, check boxes — but I won't push my luck more than I am at the moment. :rolleyes: