Buttons for Archos will let you change the width of the buttons on the bottom or right of the screen (or remove them entirely if you wish, by setting the width to zero) as well as to rearrange the contents of the buttons.
You can even add new buttons with contents like "Camera" or "Volume +". These buttons should work, but they will have no icons due to limitations in the OS.
I have reason to think this doesn't work on the latest Gen8 firmware.
