Concerning the supermarket, I just searched on google for big enough "supermarket shelves" images, and then I reworked them in GIMP (open source photo software).
Then, I printed them in normal quality on A4 sized white stickers. Then, I cut them with cutter and xacto knife, and glued them on cork.
For the commercial posters and front "powermarket" sign, I used open source software Inkscape, wich is really great to make print graphics. I also used free fonts I downloaded from Dafont website.
For the other buildings, I'll do the same. Mixing inkscape vector and gimp bitmap design tools, and images from internet
