Cristobal,

There is not way to do this with Forms out of the box, but you can use Javascript to accomplish a similar task.  A quick google search found some font-image generators and the one I chose to use is Fontmeme.com.  Using this site and embedding your text in the URL displays an image in a custom HTML Field using the Javascript below:

$(document).ready(function() {
 function imageSigned()
	{
	var userName = $('#q3 input').val() ; //This is the field where the user's name will be typed
    var signedImage = "<img src='http://fontmeme.com/embed.php?text=" + userName +"&name=learningcurve_tt.ttf&size=100&style_color=15155E'>";//The source to generate the 'signature' you can choose whatever fonts are available
	document.getElementById("q2").innerHTML = signedImage; //This inserts the image into a custom HTML Field (q2)
	}
  $('.name').change(imageSigned);//This initiates the code once the name field (q3) is changed
});

Note: You can find the different fonts, sizes, etc. HERE

You can see my sample below:

Hope that helps!

-Nate