Instead of using <img> tags for your icons, you can use icon fonts on <span> tags (which offer some advantages such as not having to create a sprite, being able to scale icons up/down without degrading quality...).

However, by using an icon font you give up the <img> alt attribute (that attribute can help you with SEO). There is a way to add text to the <span> and hide it, but I wonder whether this is recognized / penalized by Google (as it seems to go against the quality guidelines).

Are icon fonts bad for SEO (i.e. by using icon fonts you give up the alt attribute) ? Would inserting text in font icon tag and hiding it with CSS (text-indent: -9999px) be recognized / penalized by Google ?