You could also use a graphic tablet and “draw” the design with the pen – like this one here:
http://www.amazon.com/Wacom-Bamboo-Pen-and-Touch/dp/B002OOWC3S/ref=sr_1_1?ie=UTF8&qid=1351521648&sr=8-1&keywords=Bamboo+Pen+%26+Touch
They even have a free drawing software you can download from the website (http://bamboodock.wacom.com)
I have a friend who uses this to draw mock ups for her grafic design projects and she loves it!
I consider buying one for myself for some time now…
Mirjam, Cake Couture Cologne, Germany
