You may have noticed that the PSP background changes colors every month.  (if you havent noticed that yet, trust me on this one)  Therefore it makes sense that there are 12 files that you can modify.  For the purpose of this article we are just going to replace one, June since that is the month that we are currently in. (at the time of this writing). 

The files are to be named as follows:

01.bmp = Jan
02.bmp = Feb
03.bmp = Mar
04.bmp = Apr
05.bmp = May
06.bmp = Jun
07.bmp = Jul
08.bmp = Aug
09.bmp = Sept
10.bmp = Oct
11.bmp = Nov
12.bmp = Dec

Step 1. Create your Image
Go ahead and use your graphics editor of choice be it Photoshop, The Gimp, or Fireworks or whatever.  Make an 300x170, 24bit BMP file that is less than 150k that you want to use as your background.  If you have an existing image that you want to use, you can simply shrink it down to fit.  Save this image as 06.bmp (by using the information above we see that 06.bmp corresponds with June, our current month.  If you are reading this and it is a different month, change the file name as required)

Step 2. Connect your PSP and transfer the files
Connect your PSP to your computer to access the Memory Stick and place the homebrew software. I will be using a standard USB-A to USB-MINI B cable.  If you need help connecting your PSP to your computer, check out the "Running Homebrew on 1.5 PSP"  Once again, my PSP when connected to my computer is E: -- so from now on, when I refer to the E: I am referring to my PSP connected to my computer via the USB cable.

Download the PSPersonalize file above and extract it to your desktop.  You will notice that there are two folders inside: PSPersonalize and PSPersonalize%.  This is a homebrew applicaton that allows us to replace the backgrounds on our PSP.

With your PSP connected to your computer, Browse to your E:\PSP folder. (assuming that your PSP is E:)  If you dont already have a GAME folder go ahead and create it. (E:\PSP\GAME)  It is in this folder that you are going to want to copy both the PSPersonalize and PSPersonalize% folders that you expanded earlier.

    We now have to place our images on our memory card so we can flash them...  Common sense would tell us that we need to place them in the E:\PSP\GAME\PSPersonalize directory, Right?  Wrong, we will place these images at the root of the E:\ Once you have your files (you can place 1 (like we did above), 2, or as many as you want -- up to 12 of course.  MAKE SURE YOU USE THE NAMING SCHEME ABOVE.  For example, our image is called 06.bmp because I want to replace the june background.

Now that you have the images on your PSP Memory card, we are just about ready..

Step 3: Change your background!
Unplug your PSP from the usb cable, and go to the "Game" section, once you are there arrow down to your Memstick.  Select it by pressing 'X'.  Arrow down until you find PSPersonalize, and select it again by pressing 'X'