Penn Libraries' subscription to Artstor (PennKey login) provides access to over 300 image collections representing disciplines like fine arts and art history, architecture and interior design, landscape architecture, and anthropology and archaeology.
There are three types of collections in Artstor.
Artstor also provides subscribers with access to the Images for Academic Publishing (IAP) program, high resolution TIFF files free to use in scholarly publication. Be sure to follow Artstor's permitted and prohibited uses and get additional support using Artstor Guides, including about copyright.
Be sure to read the copyright or permitted use pages of each site and find appropriate contacts for permission to use images you find on these sites.