Just as with traditional SEO, the key to getting images to appear is to make them as relevant as possible with as many indicators of quality as possible. Host the image on your own domain. Most images are served from individual domains and not services like Flickr. The page on which the image appears should be on your home page or only 1 link away. Lots of images are not found on home pages. Lots of images are found on pages only one link away. Include the image on a page with several external links. Include the image on a page that receives lots of internal links. Decide what search query you want the image to appear for. Include the search query in the H2 or H3 tag preceding the picture. Include the search query in the Title of the document. Include the search query in the text immediately surrounding the image. Include the search query in the ALT=Text (alternate text) and LONGDESC=URI (link to long description) of the image tag. Include the search query in the file name. Using an image editor, include the search query in the image file itself. Not on the visible image. In the image's text fields. (In Gimp, the comment field. In Photoshop, file info.) Do as much of the above as you can without appearing spamalicious.
Great techniques there. Ive made a post on my blog about optimizing images for traffic you may want to check out.
Since I posted the list I'll answer this. Do I know? No. Then why did I list it? If Flickr/Yahoo! can grab this info then so can Google. Most Popular Cameras in the Flickr Community If Google can capture it they can use it. It's one more signal of quality you can add to the mix. It's also on the bottom of my list because I doubt it is a major factor. If you want an idea of how Google thinks about this stuff you should read their recent patent application for blog search. IMOHO, it is much easier to rank documents than images. Also, FYI, I've had well placed images in Google Image Search since its inception and it has never driven sales.
There's actually a great tutorial on optimizing for images. @ JimKarter For #11, placing text on the direct image will not do anything. And putting text on the comment will probably have no effect either since googlebots will be unable to read that. Nice site drig.