Customizing 404 Page
Theme Options > Appearance > Layout > Content / Page / Post : Custom 404 Page option will be useful in this case. But, first create a 404 page as you desired to simply select it from this option.
Theme Options > Appearance > Layout > Content / Page / Post : Custom 404 Page option will be useful in this case. But, first create a 404 page as you desired to simply select it from this option.