I can certainly relate to this. I started scripting for very obtuse reasons, and quickly started seeing things everywhere which I could apply a little code to and improve my life.

You can have fun with 'em since they're public domain (:

Note 1: The metadata, such as title, author, etc. seem to be missing. If anyone knows of a collection with all that included, let me know (it's not in the EXIF either, I spot-checked).

EDIT: aha! Here is metadata, which you can correlate to the image files: https://github.com/Wumms/pomological

Note 2: I saw this in the MARC catalog record:

  Use of the images in the U.S. Department of Agriculture Pomological
  Watercolor Collection is not restricted, but a statement of attribution is
  required. Please use the following attribution statement: "U.S. Department
  of Agriculture Pomological Watercolor Collection. Rare and Special
  Collections, National Agricultural Library, Beltsville, MD 20705"

This actually inspired me to go out and start (slowly) cataloging mostly historic 100+ yr old landscapes that were locked behind mostly non-US pay-to-access (cough British museums cough), and write a flurry of emails to institutions encouraging uploading high res versions. I'm contemplating a project to put historic paintings "on the map", depicting their geographically represented locations (when applicable), giving a window into the past. Maybe I should circle back on this effort to get more paintings released...