A treasure trove of animation images is available at the Flickr Sets of Animation Resources. The sets are comprised of screen grabs from the Golden Age of Animation, primarily from the 1930s and '40s.
There are sets of walk and run cycles, such as this one from the Disney's 1933 Silly Symphony "Three Little Pigs."
Special effects sequences are broken down frame by frame so that you can study them in detail.
You'll find well known characters such as Elmer Fudd and Bugs Bunny, and also lesser known characters.
The sets also include cartoon-head-turn sequences, Muybridge photos, pencil tests, dance reference, lip synch reference, animation backgrounds, and exposure sheets. Many of the sets are identified by the name of the animator who did them. These would be inspiring not only for animators, but also for character designers, illustrators, and lowbrow surrealists.
Animation Resources Flickr Sets of Stills
Animation Resources also has an Instagram feed where they show a short animation clip and then play it slowed way down so that you can analyze it.