Still its infancy, UIzard is on a very promising route to be able to do quick UI discoveries and mockups.
One of the most exciting feature of UIzard is the theme switcher: upload any image (screenshot, moodboard etc.) and your existing prototype will get a brand new look. I tested it, really works as promised.
Uizard uses powerful deep learning algorithms to generate beautifully designed themes from the images you upload.
(It can convert hand drawn sketches into designed screens too.)
