How can you set a picture for a background on a palm centro phone for sprint?

i got the palm centro a few months ago, i recently saw today at work that a co-worker had the same phone, but she had a picture for a background instead of the homescreen with all the applications on it. i have not been able to figure out how to set a picture for a background and not have the homepage there. if anyone can help me out and give me directions as to how to make a picture the background on the palm centro it would be veryyy much appreciated, thanks!