I have build several billboards of different type for use on the Zity Edge Layout.
What is the size of a billboard? And where to find ads and posters that can be used on the billboards? As anything else, Google and the internet is the answer.
I found an interesting article describing the different sizes used in USA. What Are Billboard Dimensions? | DASH TWO
And searching for billboard ads gave me a lot of interesting results, where I composed a page with a lof of different ads that I would like to use. Its not easy to always know the correct year when an ad was used, but movies, like E.T, was released in 1982 and would fit my timeperiode. And the 1983 Thunderbird ad.
And using Photoshop to manipulate the images to get the correct aspect ratio and size on each image.
The billboards are build using a 1 mm cardboard piece, cut to the correct dimensions, and different dimensions of Scale Lumber, from Northeastern and other vendors.
After making a drawing and create a jig for the construction, it's easy to create several billboards in a short time.