When it comes to using sprite images for icons that are linked without any associated text, the best method in terms of SEO is up for debate.
Here are a few different examples of how the markup could be implemented:
Option 1: Individual Images
<a href="#">
<img src="icon1.gif" alt="SEO Text" />
</a>
Option 2: Sprites with Title Attribute
<a href="#" class="sprite icon1" title="SEO Text"> </a>
Option 3: Sprites with Title Attribute and Indented Anchor Text
<a href="#" class="sprite icon1" title="SEO Text">SEO Text</a>
Alternatively, there may be other methods to consider as well.
Thank you!
EDIT:
Another potential option is:
Using Transparent Image with Alt Text along with sprites
<img src="transparent.gif" class="sprite icon1" alt="SEO Text" />