Here is how you modify some icons/graphics:
*backup with nandroid first*
1. Pull the framework-res.apk file:
$ adb pull /system/framework/framework-res.apk
2. Extract the apk file with archiving program (winzip or tugzip)
* keep original framework-res.apk handy for later *
3. The images you are looking for are in /res/drawable-hdpi
4. Modify your images as you like.
5. Once you had all the images ready, open up the original copy of the framework-res.apk file with (winzip or tugzip), drag and drop your new
images into the correct directory. Close archiving application.(The purpose of just dropping the images into the apk file is to save you time of having to repackage the extracted framework-res.apk file and having to sign it)
6. Push the apk file back to the phone:
$ adb push framework-res.apk /system/framework/
(you may need to make the /system partition writable)
mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system
7. Once the file is copied you will see some apps on your phone die, like android market. Just reboot your phone and you should see your new images.
Note: Check out google dev site for info on the Draw 9-Patch.
Draw 9-patch | Android Developers
Hope this helps.