I recently came across a really great online archive of public domain vintage and antique images... not sure how I hadn't stumbled onto this site until now. The site is called Vintage Printable. They have an amazing collection of antique botanical drawings and nature studies, scientific charts, book covers, and vintage photography. Great for reference and collage. Another great website to find antique and vintage imagery is the New York Public Library Digital Gallery (they have everything -- from antique textile pattern books, vintage hotel menus to antique images of ocean flower cyanotypes). Below are a few of my favorites from Vintage Printable.