Sort of along the idea of copying the masters, you might be interested that the Smithsonian has launched an open access portal to its collections. https://www.si.edu/openaccess
Loads and loads to browse there, including high quality images of Homer, Hopper, Whistler, and other famous watercolorists. But I found just browsing through watercolor as a topic some extremely interesting pieces, not on display. There were some very interesting ones done during the wars. Stuff you don't normally see, and probably never will as they wont be put on display.
They have also done 3D digitization of some objects, good if you want to see something from all sides.