Helpful links to refer to....
Free Backgrounds
Choosing Coordinating Colors
Vectors "n" Art
Using vectors and art cannot only make your site look good, but can make it look like a professonal designed it for you. However using vectors can be tricky at times, so make sure you know what you are doing and how it relates to other things on your website before placing it on there.
Direction Summary Website
I used this website when I was unsure of how to change a color in the begining of class and it has been helpful for many other things since then. Maybe it will help you to!!!!