header image

I want to use a header image, instead of header text. however, I don’t want to use one that’s 1280×250. I would like it to be 635×100.

I changed the max-width of #wrapperheader to 635 and that changed my width, but I can’t figure out how to change the height.

I would also like to align it to the left side of the screen.

Are these things possible?