In the spirit of Tomkat's More Signs thread...
Popular Science & Google Books have "teamed up" with a period resource suitable for "photoshopping" signs and billboards -- the bonus is Popular Science goes back over 135 years -- meaning we can even "time travel" to a priceless "historical - technology - cultural attitude" for our exact layout year!
Example: I went to January 1956, and a De Vries ad showed a (perspective drawing) street corner picture of their headquarters, which can easily be adapted as a local department store building/billboard advertisement -- using a screen-capture program (Faststone, Bug Shooting, Fireshot, etc.) plus a photo editor (M$ Paint, Photoshop, IrfanView, PhotoFiltre, Paint-net, Photo Commander, Gimp, etc.).
Hopefully this can help to add a little something extra for your period attitude & layout signage. Anyone else run across a layout-extra period resource?
Conemaugh Road & Traction circa 1956