Create high quality, very costly, hand made jewelry based on TTC tiles. Make one set for each traditional old school tile colour and utilize the standard subway tile proportions. maybe do some one offs, a ring here, a necklace there in the incidental yet associated colors of the TTC.
The bracelets could be sterling silver. I picture each link to be a chunky high gloss silver rectangular brick with one open side, into which is sunk a ceramic mini-tile in the same proportion and colour as a actual subway tile.
Now I can picture a pretty huge ring as well, portrait style in a heavy silver setting. You could easily do more pieces as well including a necklace and pendant/obelisk earrings. Make it very chunky rather than elegant and petite. Maybe each element is the same size.
Green, grey, yellow, orange, flesh, white, doorway red, safety strip yellow, turnstile stainless, etc ad