There has been a lot of discussion on the use of alt attributes in images to improve rankings. The concensus is that for the most part these only factor in when used in an image that is linked to an internal page or possibly another site. While this post is not intended to bore the more experienced experts, it does discuss the limitations of these attributes, something novice and expert could review a like. A little different spin on a long debated topic being discussed over at Highrankings. Worth a quick read.
Check out Alt and Title Attribute Limitations