Landing Page and User Authentication

I am creating a site for my Poker Buddys Home Game. I want to be able to create a Landing Page that will simply be White with our Home Games LOGO in the middle and username/password to logon to the internal site. What them do you recommend that will allow me to just have a black canvas or Maybe a POKER background with the Home Game Logo (PNG) and right below a field that will have Username/Password to access the internal site. What plugin can i use for the user authentication to logon? Thanks.