APM logon page - central space customization

Hello guys:

Please, I hope you could give me some guidance for the customisation of the logon page for the APM v 14.1.0.2.

I have managed to modify the header and the lateral segments and my boss is agree with that. But, I would like to add a html code containing a web page of my organisation in the central space which is too big to be empty (please, see attached image). I want to achieve this in the easiest way as I have the other segments already pretty good. I do not want to use the process located in https://devcentral.f5.com/s/articles/Customizing-APM-end-user-login-page-with-APM-Advanced-Customization-Templates as it makes changes in all the logon page and I just want to add some code for the central space to show a web site.

Thanks a lot in advance.

Omar