Just think: most of what the library gives you access to is words--books, articles, databases. They're full of words, and you use words to locate what you need from that collection of words. Images (and visual media in general) often don't work the same way. They might be described using words (known as metadata, which can consist of the title, creator, technical specifications, or other information about the information), but generally those are going to be more limited in scope than, say, searching the contents of an entire book to decide whether it's relevant.
And yet, most collections of images ask you to use keywords to locate items.
So to find images, it's a good idea to switch up the approach and be aware of the way the images are described and organized just as much as you're thinking about what types of images you're looking for.
While there aren't a lot of rules that apply to every single image collection, there are a few that are broadly applicable:
What does this mean in practice? ARTstor, which a mostly closed collection available through the library, can offer some insight into this.
Let's consider ARTstor's landing page. We see a main search box and a very limited number of top-level options.
Let's say we are interested in images of farm workers in the United States. If we take the search bar at face value, we might be tempted to include a lot of search terms in order to get narrow results. Something like "farm workers" "United States". But what about alternate terms besides farm workers? Or what about images described in such a way as to take the United States for granted--or rather, those that get more specific in naming a place than just a the country? Also, is there a specific medium we're interested in?
ARTstor's advanced search lets us control for region, chronology, and medium. We can use these filters to ensure we are sweeping all of the United States and focusing on mid-twentieth century. Using flexibility with our keywords and synonyms, we can use in combination with filters to find a number of relevant results that document the development if migrant farm labor in the United States.
But what about use? Let's now say that these images are going to be a great asset for an upcoming publication on this topic and we'd like to reproduce them. The following are all of the results of the search:
ARTstor then allows us to only display images from their public collections (the others are protected by copyright and require an ARTstor subscription to view):
It's still a good idea to take a look at the Rights statement that accompanies each item in order confirm if and what type of reuse is permitted, and who to contact to get more information.
The following are a selection of image collections, libraries, and archives that are generally intended to be used for study, though some may be in the public domain or licensed for reuse. For images explicitly licensed for reuse and modification, check the next tab.
Note that many image databases linked elsewhere might include open access and/or public domain images and often are able to be filtered accordingly. The following are resources that primarily feature images licensed for reuse and/or that are in the public domain.
Be sure to check in the general art image databases for design-related content, too!