The use of large-format images, so-called hero images is a relatively new trend. Some people ascribe Apple introducing, others suggest that the tendency to use of large-format images always was and was long suppressed only by weak-breasted Internet connections.
With the increase, access to better internet connection use of large images will also grow. Hero images traditionally use at the header of a web page and introduction. So this gives good first impressions. Parallax designs have expanded the use of hero images on other page segments.
For your inspiration, we have dug 25 free-range Hero templates from the Web. Some represent more complex PSDs with additional levels, others are simply great pictures. Anyway, you can get a good idea how to use hero images on your web projects.