Does Google take into account the URL of an image when searching e.g. could domain.com/cats/lolcatz/m.jpg appear in a Google search for 'lolcatz'?
you could do this: original img url is: yourserver.com/img/bla.jpg link it from everywhere like yourserver.com/img/bla.jpg?image-content-related-keywords-here behind the ? you can write anything
thats old knowledge... look this example: http://www.google.com/search?q=site:rapidlibrary.com&num=100 this site has 113 million pages in google and ranks among top 200 in alexa... all with dynamic urls.