It is very permitted, possible and perhaps even easy. It's not my style, but I did go into the customization area and ninetydegrees has done a very good job of making it customizeable. You can change colors here:

http://www.dreamwidth.org/customize/options?group=colors

And images here:

http://www.dreamwidth.org/customize/options?group=images

Aside to designer: wow, ninetydegrees, something this lickable yet customizeable without making new images and such = A+