I noticed today in Zuerich, Switzerland, that many posters come in different sizes, and proportions, the most common combination 90 x 128 cm for the small portrait size, and 270 x 128 cm for the landscape size (see the site of the APG posting company for more information on standard swiss poster sizes). Below are some examples.

for a newspaper

for an agricultural fair

for an african circus

for bio food from a supermarket chain

for a furniture exhibition

for health care incurance

for health care incurance