Well, it's not really a mockup, it's already an applied theme to my Lubuntu desktop, fully functional and installable. The mockups are a tricky question, because of their complexity and inability of some visual improvements (due to coding limitations), like this:
Now let's return to the real world. I don't know if this theme will be the next one for the 11.04 release of Lubuntu, but anyway it could be a nice theme. I must be voted, aproved and accepted for the (growing) community. It's based on Zuki Blues, by Lassekongo. Have a look and say what you think (screenshot with and without shadows).