edit uEnv.txt. Replace console=tty0 with console=/dev/null
Note the tux logo is not removable (it's compiled into the kernel)
Custom splash:
In theory you can use plymouth, but I never got it to work properly.
You can also use something like FBI (frame buffer image) but I never got this to work properly either:
Enable insserv:
sudo ln -s /usr/lib/insserv/insserv /sbin/insserv
Do this:
http://www.edv-huber.com/index.php/problemloesungen/15-custom-splash-screen-for-raspberry-pi-raspbian
After:
update-rc.d a_splashscreen defaults 98 02