One of the most common SEO techniques is using alt tags for your images which of course is a good practice anyway.  The basics behind the principle is to put keywords your targeting in  your image alt tags.

Darren Rose writes

Over the years SEO techniques have been developed to abuse this fact and webmasters have ’stuffed’ their ‘alt tags’ with all kinds of keywords - however Google has found ways to combat this and treats such strategies as spamming their bots now - however it is still legitimate to put keywords in you image tags and I would recommend that you do (within reason).

Lets just say for instance if I was going to target gamers playing Age of Conan.  I could use the below image to help them find this article by using a quality set of relevant keywords in the below image's alt tags.



Now my code reads

<img width="550" height="413" align="middle" src="Image/ageofconan.jpg" alt="Age of Conan Game Screen Shots" />

Loading your images down with non-relevant keywords could cause Google to penalize you so be careful.

I hope this was helpful.