This is how to change your background to a more cool and colorfull one like the included pic attached below, + keep the cool wavy lines too
Right then.
First download the attached pspfilerv2.4.
Create a image in .bmp format with the size being 60x34 and has to be named "01-12.bmp" without the ".
Next go to theme settings on your psp, then to theme, and change it to original. It wont work unless its set to original
next, put the 01-12.bmp image you made in the root of your memory stick.
start psp filer, once its started press L+R+D-Pad-Left
now navigate to your 01-12.bmp file and press square then x. press circle now to copy it into the ramdisk.
once done press circle again.
press start twice (should say file:[flash0:/]) at the top now.
go to vsh/ and press circle. now go to resource and press circle. now then, press cross/x then press triangle, press circle to confirm overwriting the previous bmp file.
and your done
press select + Start to quit to the xmb and enjoy your new background
for 3.03oe users just start up recovery mode, click advanced then toggle usb(flash0).
and in windows navigate (your psp directory) to vsh/resource then just paste/replace the current 01-12.bmp file with your new one.
i have included the default image just in case you make a mess of it or dont like it.
Tested on 3.03oec [/U][/B]
enjoy
Same method with a few changes works for custom gameboots too on 3.03oec ive just done mine now using the same method but with a gameboot.pmf file. Its in the same directory as the background image, so you should be able to work out how to do it
I made this guide to help others but take no responsibilty if your psp bricks as a result.