Tempered glass unless intentionally abused won't break easily.
(sample site below...using as a reference)
»www.dullesglassandmirror.com/cus ··· lves.asp
Looking at your picture, I would (drill-anchor through tile) put two side mounts and two back mounts to hold a glass shelf.
You would get light and still have space for storing shampoos, soaps, shaving stuff...
I have a glass shelf (tempered) in my bathroom and its fine (though not in the shower as I already installed a two shelf insert from swanstone)--