changing background images in themes..?

[knowrites]

is there anyway for me to change the background image in a theme?
i've tried switching file names around to make it load different images, but everything i try just ends with a blank backdrop.. any help?

[Chronon]

You can set a properly sized .bmp to be the backdrop via the Context Menu.  This is mentioned in the manual.  Note that if the code for the WPS specifies a background image then this will still be displayed on the WPS.  You can either edit the WPS to point to the new image, remove the reference to a background image, or choose a theme that does not draw a background WPS image (e.g. the default Rockbox theme).