I have also considered making one more like the one you describe that you have created and using Christmas lights on it as you have. Or, outlining a shape on plywood using
Christmas Lights. I am still considering the best (and prettiest) way to go. I am glad to hear someone else has done this so that it is doable.
A neighbor has constructed letters outlined in lights that says "Happy Birthday Jesus", no other ornaments, decorations, etc. just that sign which hangs in their picture window, big and bright for all to see!