It depends on what type of motherboard you have and if it supports the ability to chage your BIOS diagnostic screen into a simple bitmap.
Keep in mind though that the bitmap will probably be limited to 256 colours.
Even my old Socket370 QDI motherboard's latest BIOS update gave the ability to change the 'diagnostic' screen into a swanky picture.
A good idea would be to reply back to this thread and let me know what manufacturer made your motherboard.
If you don't know who made your motherboard - use a program called SiSoft Sandra 2001 from Downloads.com
The next step would be to visit your motherboard manufacturer's website and download the latest flash file to update your ROM chip.
This may then give you the ability to change your BIOS post.
If your m/b doesn't support it however, then there is no chance of us being able to do this - apart from purchasing a new motherboard!
I hope this helps in some way