1) Department store decorator 2) Department store employee 3) Store worker 
Window dressers arrange displays of goods in shop windows or within a shop itself. They may work for design companies contracted to work for clients or for department stores, independent retailers, airport or hotel shops. Alone or in consultation with product manufacturers or shop managers they artistically design and arrange the displays and may ...
[n] - someone who decorates shop windows
window trimmer noun someone who decorates shop windows