I’ve had good luck etching from the backside of a glass plate, but did it with a pretty simple image. When I bought some Ikea spice jars to try it from the front, it didn’t work as well, The laser sheared away differing amounts of glass that weren’t a problem when engraving from behind, but looked bad engraved from the front.
https://community.glowforge.com/t/weird-problem-partial-engraves-on-glass/17675