"SEO"How Good Is Google’s
Image & Video Understanding?

Google’s head of the web-spam division, (and thus SEO), Matt Cutts, answers a common question we see about web design…

“I have removed a lot of text from my site and replaced it with images. My bounce rate has dropped considerably, conversions and time on site are up. Will Google have an issue with the lack of textual content on the site? Does Google still need text? Daniel Weadley, Camberley, Surrey, UK”

You can find the site he mentioned at: http://www.google.com/webfonts

As a side note, a move towards more images and less text almost always decreases the accessibility of your site for visitors who are vision impaired.

It also can cause issues for mobile devices which may not be able to make the content of the image easy to read on the screen.