I posted some examples of this earlier this summer. (Dispatches from the front series in Made on a Glowforge)
Paint/dye/ink when engraved on the surface accentuates the depth of the underlying glass - you see the engrave and a shadow under it.
I really liked the effect of lasering from the back of the tile - the white paint/enamel that’s on it turns a solid dark black rather than ablating off. Then it’s viewable from the front but no spurious shadows.