WP Default Author

This plugin allows blog admins to change the default author globally so that when any user posts it appears under the same name.
Admins and editors can also change the default author for a single user. This setting takes precedence over the global setting.

Source

The plugin is available at github: http://www.github.com/birgire/wp-default-author

Photo Credit

Plugin header picture is taken by ólafur Jens Siguresson ojsbug@gmail.com. It’s taken at Hnífsdalur, ísafjarearsysla, Iceland