you can easily add an image or customize your contact page (or any page besides the checkout) however you like. when you go to Pages > Contact Us on the right side there is a dropdown called Theme Template. this is where you choose what template you are using. so…
go into your theme editor and at the top use the dropdown and go to Pages then press Create Template. This is where you create the page. When you are done creating the page go back to Pages > Contact Us and choose the template you just created