Hi ! I need Help please with this .. so i've got a two recesses in this bathroom's back splash .. the material that i'm using for the back splash is this

and for All sides of the two Recesses is this

so i need to put indirect like somehow in the recess "mosaic but i wanted to be hidden very well , so the one who is sitting in the tub cant see it .. and i want it to light up all the recess not only a small side ,, can anyone recommend a good ideal ?