I love stained glass! We have pieces adorning windows on 3 of the 4 sides of our house.
I had a friend who had a stained-glass mountainscape that was at least 3' x 6', but, like you, they didn't have a window to hang it over.
What they did have, though, was a sunken den, and they used large chains attached to the heavy wooden frame to hang the piece behind the sofa that backed to the kitchen/breakfast nook. If you entered from the kitchen/nook (which was the shortest path), the mountainscape was illuminated by the lights in their ceiling fan fixture. And from the pit looking out, it was backlit by either the sun or the light coming from the kitchen area.
Of course, they didn't have any kids or pets who would be launching projectiles in its direction, though.