Margins between new sections and titles are way too small, same thing goes for box sizes. Also try to make something more unique with more effort, this looks absolutely flat and numb. I can see box/border/font shadows working well here.
How did you make the figures? I've always relied on vectors for minor artwork. I personally know some people who can do it, but I try and fail. (Using PS CS3)
Great design! (minimalism seems all the rage these days)