Is this what you mean:
You have a text link e.g.
<a href="mailto:[email protected]?subject=Subject&body=Please enter
message here">
Email Me</a>
and when the mouse goes over this link you want a picture to appear ?
If so, just use onmouseover:
<a href="mailto:me@myaddress?subject=Subject&body=Please enter message
here" onmouseover="showpic()">
Email Us</a>
and write a JS function showpic() to display the picture.
Of course, writing the function is the crux of the matter.