"Faux" pas?

I've been wanting to do something with the glass block windows on the front of my house for some time--my husband insists that they're energy efficient, but these long, narrow windows leave much to be desired. I had a brainwave when I saw this tile mosaic on Apartment Therapy--wouldn't it be fantastic to create a "faux" window pane with glass tiles and put the faux window over the other one? Then I'm happy on the outside, and we still keep the efficiency.

I'm thinking I might use some clear caulk or glue to attach the tiles to a piece of glass or plexiglass, then grout and mount it over the window. What do you think? Anyone ever tried something like this?