It is becoming more and more important to pay attention to the images on your pages. While the search engines, as far as I know it, don’t analyze the content of the images they do use the alt text, the file name, and the text that surrounds your images on the page to influence the page’s rank.
Make sure that the alt text for your images is descriptive and contains keywords. Which raises another guideline which is make sure the images on the page are interesting and relevant to the topical focus of the page.
Good: “Left + Right, LLC Web Design Company Logo”
Really the same advice applies for the filename as the alt text; descriptive and use keywords. However, with the filenames make sure to use hyphens and not underscores to separate words.
It is a good idea to add captions or make reference to the images in the content surrounding the images. Again be descriptive and use keywords here too.
Lastly, optimize your images. While that might not affect how the image makes your page rank directly it will affect the speed at which your page loads and that can effect your page rank.