I think the glass backsplash is not a good idea. As snowy89 pointed out, you will have trouble mounting most of the toilet accessories on the walls. Cutting holes through the glass means your contractor will probably use silicon to patch the exposed holes after mounting the accessories. This can be hard to maintain if the silicon is not smoothened out. The biggest hazard is if someone loose his grip on the hand-held shower head, it will back swing and hit hard on the glass backsplash. Too dangerous...