Your Sony PSP background changes from month to month, however you can make the background stay one color. Here is how.
This trick is only applicable with Version 2.0 firmware or later:
1. Go to Settings > Theme Settings, hit the X button, select Theme, hit the X button again.
2. Select a color from the menu that is shown on the right. The colors will change when you select any options in the list. However if you choose Original, then the color will change each month. Then select the X button to make your selection and your PSP will permanently have one background color.