I rewrote my Tumblr Importr to be a little easier to use and do a better job of downloading all the images off the Tumblr CDN (this often stalls and needs to be rerun a couple of time to get everything, I guess because Tumblr blocks scrapers).
Check it out at https://github.com/carlmjohnson/tumblr-importr.
The sample theme is still extremely barebones. Anyone who wants to make a better example theme is welcome to open a pull request.