Art from the 1950s, 1960s, and 1970s pops up from time to time. Newer art from the 80s, and 90s is reasonably easy to get from the Warner stores or from galleries. Reproduction art Limiteds and sericels are quite plentiful, so you should have no problem finding reproduction art of your favorite characters. Production cels are relatively easy to get. Selecting a favorite cartoon or scene is more difficult.
Drawings are semi-easy to get.
Master grounds, early Tracey Ullmans and first season pieces are hard to find. Reproduction art does exist, although they do not produce too many editions. 70s, 80s and 90s is easier. You stand a good chance of getting a nice pose of your favorite character. Reproduction art is not too hard to find.