2014 update: This is quiiiiite old and while I wouldn't recommend trying to learn too much from it, it's kinda cool to look at and does point out some subtle differences between the species. Please; go study from photos! This is a very rough, wonky, specific guide!
Keep in mind that this cannot teach
you to draw bigs cats! The purpose of this is simply to show the subtle differences between each species. To learn to draw big cats, you need look at plenty of references, go to zoos, study muscle and bone structure, and practice a lot!
nonetheless, i hope you find this helpful!