Suggestions regarding your money:
Perhaps give the large "50" a thicker stroke; to increase visibility.
Give the "FIFTY" text a double outline (one light, one dark), to enhance visibility.
Consider adding another serial number in an open area.
Perhaps add a seal (bank or governmental) in one of the open areas.
Flip the portrait so he faces toward the center of the note; to draw the viewer's eye smoothly across the note, left to right.
I encourage you to peruse Ron Wise's big collection of banknotes, for ideas:
http://aes.iupui.edu/rwise/notedir/mappage.html
Look at what other nations are doing, read up on banknote design principles and anti-counterfeiting measures. If you want.
I'll post some of the stuff I've done later tonight.
-Mike