The short answer is Not...
Here at SEOmoz we ran some correlation data last year to determine the answer to this very question. The result was that we discovered simply using your keywords near the top of the page in a larger font will yield you much the same results as an h1 tag. You can find the Whiteboard Friday where this was introduced here: http://goo.gl/9IJ0X
Also, I strongly encourage you to stay away from most image replacement techniques as they will end up causing you more harm than good. For images please use the ALT tag
