Yahoo just threw an interesting component into the mix related to image SEO.
If you do image searches at Yahoo you will now be given filters which connect directly to Yahoo-owned Flickr.
That's right, Flickr images will rank well in Yahoo because Yahoo favors their own products. Makes sense, right?
You can read the official announcement on the Yahoo Tumblr blog.
As you see in this screenshot, when you see the image results, when Flickr photos exist and are optimized well, Yahoo will display Flickr images above organic results.
Do a search for the word "sunrise" and you will see an example.
If you want your photos to show up in Yahoo image results, via Flickr, then make sure you optimize each photo for the appropriate keywords.
That means the image title, the image description and the image tags used must all be optimized for the keyword you want the image to rank well for. Note that including dozens of tags does not mean your photo will rank well for each keyword.
As the Yahoo/Flickr image ranking algorithm becomes understandable we will try and share Flickr SEO tips.