A large image is definitely an impact in a design, be it a newspapaer ads or just the article. The same goes to web design. Large background image has been a trend recently. More and more websites are joining this large background image bandwagon, and you should too!
Have you ever been in the situation where you have uploaded a large image, for example 700px width, however it still appears to be very small when inserted in the post? If yes, most probably because you overlook the option to select image size before inserting into post.