Header Image Size / Sizing Problem / Aspect Ratio / Cropping / Distortion

I like this theme a lot, but I cannot get the header images to display properly.

I have tried using the coding technique described by webblish in a different thread here.

I have also tried to size the pictures the same as the mountain-scene image that comes with the theme. (That picture is 1440×500).

Neither of these work, however. My images are distorted, cropped incorrectly, and look bad. I also noticed that dimensions of the images displayed on the site seem to be different between home page and other pages.

(My site uses pages instead of posts, if that is a factor.)

Any solutions?