Make PHOTOS fill full width of content area/post

Hi Everyone,
You all have been so helpful. I recently learned how to expand the width of my content area on a Coraline theme to look like this: http://bleubirdvintage.typepad.com

The writing in my post expands to fill the full width of the post/content area, but the photos do not. How to get the photos to be large and line up with my text every time?

Again I’m aiming for something like this: http://bleubirdvintage.typepad.com

Thank you!