@fred-fred You can customize the templates (eg macro body in helpers.ftl) in your theme like this:
[#if application?? && application.name?? && application.name == "MyApp1"]
this is myapp 1 login screen
[#elseif application?? && application.name?? && application.name == "FusionAuth"]
this is FusionAuth login screen
[#else]
this is something else
[/#if]