Single Post Layout

Hey Tom, hopefully last question for a while! I've got my main blog homepage set up exactly how I want now...(with images above the post text). Just wondering about one last thing... Is it possible to set out the individual post pages something like this?
Or do the header images always stay above the post... hence why they are called header images!!

I guess I just wanted to control the size and position of images once people click on the post. Although I'm thinking I can only do this if the pic is in the post rather than the header image?

Thanks again for all your help