I am working on that for the company I work for. Mostly, using long tail keyword G Search and G Image Search, downloading, and then modifiying the image name some, then upload under our Flickr and Picasa accounts. Also, all blog entries have at least one if not three pictures with longtail keywords. These are uploaded to our hosting account.

Setting up a image marketing linkwheel would help, as well, I just haven't had the time to do that yet.

Nothing black hat about that, sorry, but basic stuff if you didn't already know it. I'd be interested to hear more, of course.