a collection of pictures of signs posted at the entrance

Quick answer：

This refers to a collection of images showcasing various types of signs that are commonly seen posted at the entrances of buildings, stores, or other establishments. Such signs often serve as a form of advertising or informational display. They can range from simple, handwritten notices to professionally designed, illuminated signs. Collecting these pictures can be of interest to graphic designers, advertising enthusiasts, or anyone studying urban design and signage.