Find sources - start with the Research Collections on the Archives of American Art's website. Copies of most of our microfilmed collections can be sent to your school or public library at no cost to you! Just let us know, and have your librarian submit the form at www.aaa.si.edu/askus/interlibrary-loan
Interviews are a great source of quotes, first person accounts, and some audio clips, check out the oral history collection, many of which are transcribed online and in the public domain.
We have released several hundred WPA images on Wikimedia Commons that are in the public domain, but you might find a low-res image for your article to be uploaded to Wikipedia in our Image Gallery.
Transcribe a letter on Wikisource. Just make sure it's in the public domain!