To change your page theme/background select edit page appearance tab on your page
You'll then be taken to page appearance settings page at the top of which will be this section to select pre-set themes
Further down you'll see this section which allows you to personalise page colours and, where arrowed, upload images to display in background.
Dont forget to press ' save at bottom of pages to keep any changes you've made.
You can also use the text box on your page ( and these text boxes ) to further pimp up your page . One of the easiest ways to post pics is to upload them to AllYouCanUpload.com , and then copy the code from places arrowed and paste here to display them.
If you have a Flickr account you can use the all sizes option and copy code to paste from there.These are other ways to post pics and change page colours and backgrounds but these are probably the easiest ways to do these things for most people. .