I have done this a few times. It seems you are artistic. That being the case, he's what I did. I removed the old (not antique which I would have saved) glass and purchased new. I carefully stripped the windows and left bare, covertly fixing joints to make them stong again. I then put the painted glass in, used window points and glazing. When the glazing "dried" , about a week, I painted it to look as old as the frames. Kind of a faux job of dirt and cracks, if you will. They turned out so well that I did others and used them for framing multiple pictures, one in each light.
Good luck and take care in disposing of the old glass.