A pinup girl or pinup model is a model whose mass-produced pictures see wide appeal as pop culture. Pinups are intended for informal display. Pinup girls are often fashion models, and actresses.
The term was first attested to in English in 1941; however the practice is documented back at least to the 1890s.
Many pinups were photographs of celebrities who were considered by some to be sex symbols.
The genre also gave rise to several well-known artists specializing in the field, including Alberto Vargas . (Source Wikipedia)
This page contains some examples of pinup girl paintings, posters, and prints. One of the most popular pinup girls was Bettie Page, pictured here.