Backgrounds not working, text misaligned.

Hi, I’m new to WordPress. I’ve been trying to customise the Kubrick template, by duplicating it in the wp-content/themes folder and then replacing the images with those of my own (with the same dimensions).

The trouble is that, although I have referred to the exact file names in the style.css file, the “kubrickbg.jpg” image that I replaced with my own is no longer working. All that appears on the page is simply the header image (centred), a big gap of the page background colour, and then the footer image at the bottom (also centred). Has anyone else had this problem?

Also, the text has misaligned itself – to the best of my knowledge, I set it to be centered, but all the text has moved itself to the left-hand side of the page, almost as though the layer has shifted itself. Can anybody tell me which part of style.css I would edit in order to change this?

Thanks very much.