I've found that at the moment, it's not possible to change or remove the bios Dell logo because of the bios version won't open correctly in any of the current bios customizing software. most of the software has been developed to add the SLIC keys rather than focusing on the embedded image files, though it's theoretically possible, i've not been able to get it to load the images for replacing. it always crashes when the Dell logo is referenced. the other image files are not a problem, such as the progress bar and F2 images.
will keep trying as things develop.
AND - just an FYI, according to the guys at voodoo project, if you install chameleon boot loader rc3 for example and you *don't* install a Theme, or have a Theme folder or Themes/Default folder in your /Extra directory, (and have boot graphics enable in your boot file) the Chameleon app loads embedded images, rather than external images, so it's not possible to change the images that load without either making the default theme folder, and/or specifying the theme in your boot file.