You could use it as your personal gallery. Choose a layout you like and divide content using tags.

It's up to personal preference. There's plenty of artists who get more use out of their tumblr, and plenty of artists who get more use out of their FA, and plenty who do both.

It's a pretty good alternative to furry gallery sites, with less a chance for it to randomly go down and a much simpler interface.

Plus, don't underestimate the power of things going viral. If any of your art on tumblr starts spreading around, then that's a bunch of people potentially seeing it and, hopefully, seeing links to your gallery along with it.

When artists have a Tumblr I've generally seen it used for sketches and personal work, and they put commissioned work on sites like FA.