etching

Stamp on the glass with pigment ink and carefully emboss the image. (You don't want to get the glass TOO hot or it may crack.) Spread etching cream over the area you want etched, and rinse off when done (following manufacturer's directions) use a sharp edged instrument (razorblade, spatula) to chip off the embossed image and you are left with no etching where you stamped.

I've never tried that. I guess you could give it a try with a stamp you don't use enough to mind losing. Let me know if it works.