deadsea - 2:43 pm on Jan 16, 2013 (gmt 0)
My experience supports Sgt_Kickaxe's observation. I have long been optimizing for image search using this.
The two factors that seem to matter most to image search are the pagerank of the page containing the image, and the size of the image. So putting a huge image into a high pagerank page will get the image ranked, but not leave much room in the page for other content. Knowing that links to images count the same as embedding the image you can use a different technique. Put a thumbnail of the image in the page and link the thumbnail directly to the large version of the image like this: <a href="original.jpg"><img src="thumb.jpg"></a>