SEO Friendly Images is a WordPress optimization plugin which automatically updates all images with proper ALT and TITLE attributes. If images do not have ALT and TITLE then SEO Friendly Images will add them according the options which one has set. Additionally this makes the post W3C/xHTML valid as well. ALT and TITLE Attributes are as described below:
ALT attribute is important part of search engine optimization. It describes your image to search engine and when a one can search for a certain image this is a key determining factor for a match.
TITLE attribute play lesser role but is important for visitors as this text will automatically appear in the tooltip when mouse is over the image.
For more details and download: