A demonstration on how easy you're able to set up your own tweetlr twitter to tumblr image crawler.
This demo and a tumblr account is all you need to start a full blown fulltext search on twitter for tweets containing... erm... 'cat'. And post pics that are linked in the results to the tumblelog you configured in the config/tweetlr.yml.
Check tweetlr for feature requests, bug reports and, of course, some contribution action.
Enjoy!