http://ananddrs.com/2013/09/18/remove-rpi-logo-startup/

The Raspberry Pi logo that shows during startup can be easily removed by adding logo.nologo to the file /boot/cmdline.txt

The following command can be used to edit /boot/cmdline.txt

sudo nano /boot/cmdline.txt

The source of this post came from http://www.raspberrypi.org/phpBB3/viewtopic.php?t=11642&p=417828