Entirely custom theme?

Just dumped my MSOL site (horrible, just horrible in almost every way) for WP; however I did like the way in which I was able to construct each page, and am wondering if this method is possible in WP. I simply inserted images in zones (by ‘images’ I used PS files with text, pics, ect) and more or less created each entire page in this way; only other content was navigation bar, header (in which I could insert PS file), and background (which I could also simply insert an image file). My site sells one product of which there are little variances, so I need nothing except the most basic hyperlinks and a photo gallery; is this way of building pages possible in WordPress? Thanks!