Set SharePoint Custom Access Denied Page

Using Set-SPCustomLayoutsPage command you can set the custom access denied page.

Following are the steps:-

•      Log into one of the farm WFEs as a farm administrator.
•      Open Windows Explorer, and then navigate to this folder:-C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\LAYOUTS\
•      Add a subfolder to this folder, naming it CustomPages.
•      In the LAYOUTS folder copy the file AccessDenied.ASPX into the CustomPages subfolder, renaming it AccessDeniedNew.ASPX.
•      Modify AccessDeniedNew.ASPX as desired.  To add text or other HTML elements to this page, be sure to introduce them within asp:Content tags. In the example below, formatted text has been added so that it will appear just below the "Sorry, this site..." message.
•      After completing the modification on this WFE, copy the CustomPages subfolder into the LAYOUTS folder of each of the WFEs in your farm.
•     Execute the command that will update the farm configuration database to point to the new location of the AccessDenied page: 

Set-SPCustomLayoutsPage -Identity "AccessDenied" -RelativePath "/_layouts/15/custompages/AccessDeniedNew.aspx" -WebApplication "http:/mywebapplication/"

• The Access Denied page path is now updated.
• Perform the IIS Reset activities in all the servers.