Is your client firm on that? No one really does that "enter site" approach anymore. Just a suggestion as it's a bad UX approach. Have you tried to compress your background image so it doesn't take so long to load?
I'm not sure about scaling the image. I would guess using Media Queries and use a transition to make it look smooth when the viewport changes.
As for vertically and horizontally centering, @jamy_za created the code for me. He basically used absolute positioning, setting the top and left at 50%.
I'm strictly a designer so I wouldn't want to waste your time trying something that wouldn't work off the bat. I'm sure someone will be around to help you soon. Sorry!
I'm not sure about scaling the image. I would guess using Media Queries and use a transition to make it look smooth when the viewport changes.
As for vertically and horizontally centering, @jamy_za created the code for me. He basically used absolute positioning, setting the top and left at 50%.
I'm strictly a designer so I wouldn't want to waste your time trying something that wouldn't work off the bat. I'm sure someone will be around to help you soon. Sorry!
http://www.w3schools.com/cssref/pr_pos_z-index.asp