Lightning Page Template Component Best Practices

Keep these best practices and limitations in mind when creating Lightning page template components.

Don’t add custom background styling to a template component. It interferes with Salesforce’s Lightning Experience page themes.
Including scrolling regions in your template component can cause problems when you try to view it in the Lightning App Builder.
Custom templates can’t be extensible nor extended—you can’t extend a template from anything else, nor can you extend other things from a template.

Using getters to get the regions as variables works at design time but not at run time. Here’s an example of what we mean.

1<aura:component implements="lightning:appHomeTemplate">
2    <aura:attribute name="region" type="Aura.Component[]" />
3    <aura:handler name="init" value="{!this}" action="{!c.init}" />
4
5    <div>
6        {!v.region}
7    </div>
8    
9</aura:component>

1{
2    init : function(component, event, helper) {
3        var region = cmp.get('v.region'); // This will fail at run time.
4        ...
5    }
6}

You can remove regions from a template as long as it’s not being used by a Lightning page, and as long as it’s not set to access=global. You can add regions at any time.
A region can be used more than once in the code, but only one instance of the region should render at run time.
A template component can contain up to 25 regions.

Lightning Components Developer Guide

Lightning Page Template Component Best Practices