Choosing your background for your layout is a very simple process but this is the biggest problem that makes a possible great looking Myspace page look like you know what. The process is pretty simple if you just keep in mind that you have a myspace page for a reason. You are trying to share your thoughts to the world. You will have a hard time if no one can read your page.
First thing to realize is you have already chosen your layout and you are about to install your background. The main thing you have to ask yourself is can my contents be read easily. I see too many wallpapers or clipart get in the way of the content that I just shy away from straining my eyes into reading peoples thoughts. I constantly see incorrect borders that seem to clash with a persons website. When people use GIFS for there photo pictures, there are a few that obstruct content on pages.
In short be very careful and understand that if you are going to build a Myspace background separately from your template be careful in making sure you can share yourself with the end user which are your friends, associates and visitors. They do not like straining their eyes to read your page and I know you know what I mean.