where can i gt designs for reverse glass paintings?

Answer 1

In all my years I've never seen any books on this subject, all the artists I know who paint in full colour on glass (in reverse) are self-taught. Ask a framing shop for their discarded glass and just practice!

Unless you're talking about Grisaille, which is the original technique used for "Stained Glass" and uses only one colour etched right onto the glass with a combination of pigments & chemicals. You could google that one up.