Hi 8CG,
The background image can be changed, after you enter the blog, press 'Design' on the top right corner. That brings you to a page where you must 'Customise' under the sign Live On Blog. Then, on the left hand side, you can design the blog: Layout, templates, background image...etc. I tried changing the background image, but if you don't like it you can change it. I think Ms. Avila said to have a class vote on the best picture when she gets back. So just change what you can and what you want and have fun!
-Jayden Lim