Search engine crawler / spider can't understand images, audio, video, flash files etc. your site shoud must have
powerfull keywords which user may search. For SEO, In your image put HTML
alt attribute with image src tag i.e <img src="image name"
alt="alternative text "> This alt tag is very important for search angine like google and even if you are showing image ram.jpg it will capture text from alt attribute of HTML.
For more detailed information refer book :
The art of SEO By Eric Enge, Stephan Spencer, Jessie Stricchiola, Rand Fishkin,Oreilly.