Show Schema Map is displaying blank page for users other than admin 

This is expected behavior as OOB The Schema Map functionality is allowed to users with personalize_dictionary role. 

You can customize it by using one of the solution mentioned below:

 

1. Give personalize_dictionary role to the user. 

 

Please note that if you add this role to user, the user will have high level privileges over the instance, and access to the Application "System Definition", it is not a role that you will want to easily assign to an user.

 

2. Other solution can be to customize the script include named 'ERDProcessor' (at line 495). 

 

You can make it work by updating line 495

FROM: 

if (!gs.hasRole('personalize_dictionary')) { 

 

TO:

if (!gs.hasRole('personalize_dictionary') && !gs.hasRole('<role you want>'))

Below is a link to the ServiceNow community on this. Schema map for Non-Admin 

https://community.servicenow.com/thread/165049