I'm guessing the only way "Universally" to show a message like "Welcome to my WiFi connection" is through a html landing page( redirection). I would say SMB but I believe Windows 8 doesn't allow you to "push" messages like with Windows XP. I believe you can still send message via Windows computer to Windows computer via "msg" command, but this isn't very universal.
So my question is , with out 3rd party program installed on host computer, is their another way to push a message through when guest connects to your wireless connection?