Hardware fixtures and plumbing parts....including toilet seats on the gondola.
Stickers applied to tiles would act as merchandise hanging on the wall like just like real merchandise hangs on peg board in a real hardware store.
Updated image includes a paint tinting machine.
Set pricing would see this in the 49 to 79 dollar AU range (25 to 40 dollars US), two tool wheels are required, in fact two of everything that would be merchandise on display. Tiled ceiling would add maybe another 20 to 30 dollars AU to the price.
Edit - you could use the same blue and white for Mica in the U.K. or red and white for True Value in the U.S.A. - using also the correct coloured logos and merchandise stickers.
Also this could be made into a modular design if Lego wished as well.