APM logon page - central space customization

you can add a picture there easily as pointed out here:

https://devcentral.f5.com/s/question/0D51T00007XdwuKSAR/how-to-add-an-image-to-the-bigip-access-site

but to show a other page there i believe there is no real simple way, you will need to look into the advanced customization and edit on the html / css level to make that work.