I might have experimented with making it a bit less symmetrical - maybe making it 1 1/2 or 1 2/3 tiles wide, rather than 2. But perhaps you tried that, and it didn't work so well.
The rain on the glass doesn't quite come off though - I spent a while wondering if it was rain, or just dirt. I think using water on the glass is a powerful addition to the composition, but maybe make it a bit bigger and more obvious somehow.
This is a nice shot and a good idea. I like the colors in the smooth glass and the contrasting shapes and textures. Only a 7 from me though because the specks on the smooth glass are distracting & messy. Oh yeah...great choice on the border too.