I was under the impression (before stumbling upon this solution) that the notification system was a part of the secured Android system, and would only be available for modification while rooted or modded.
This little application, Notification Toggle, gives you the power of notification power widgets without root privileges!
As far as graphical and design changes, the most likely solution is a custom ROM, and you will most likely not be able to do this without rooting and flashing a ROM.
Note: this app does not seem to enable you to change the lookout of the notification bar, which, upon second reading of the question, sounds like most of what you are looking for. i was excited about this app, so i felt compelled to share it, but i don't believe it allows for cosmetic changes to the notification bar :/ sorry!