Stick picture or drawing on glass and paint with glass paint on the other side. Use black marker for lead. Do practice on other glass before you do your project to be sure you get it right. Remember Numbers and letters will be in reverse, so will everything else, so if this matters draw the image again on the back of image and place against the glass, then when you turn the glass the right way around it will be correct!
You can draw the pattern on the glass using a dry erase marker (it's great to be able to erase mistakes so easily!) And paint with ordinary tempera paint from inside the window or glass paint on the outside
Tape pic to underside of glass use a sharpie to draw pattern . Flip back over and paint away. Or use puffy paint to make Ur lines. Hope that helps ?