To quote from the Killzone site (linked above): We Want YOU! Your Feedback Helps Us Make The Game!
Are you a die-hard Killzone fanatic? Have you ever destroyed a squad of Helghast with a single M194 percussion grenade? Can you take out an ISA platoon armed with nothing but an StA-52 assault rifle? Prove it! Download the new Killzone 2 Multiplayer theme and you may be selected for the next phase of the beta trial.
Phase three of the Killzone 2 multiplayer beta trial is about to commence, and Guerrilla wants to offer you, the hardcore fan base, an opportunity to participate. In order to provide a stable and balanced multiplayer experience upon the game's release, we need worthy soldiers to enter the online battlefield and report their feedback to us. And that's where you come in.
If you're an able-bodied PLAYSTATION 3 owner over the age of 18, enlist now! To become eligible for participation in the beta trial, simply go to PlayStation Store and download the new Killzone 2 Multiplayer theme between October 16 and 23. Your PSN account will be flagged and added to our list of prospective recruits. If you're selected for inclusion in the beta trial, we'll notify you via e-mail.
It's a win-win proposal! While we can't guarantee that every flagged PSN account will be entered into the beta trial, you'll still get an awesome Killzone 2 Multiplayer theme for your effort. But remember: we're looking for worthy, honorable soldiers, so you'll have to abide by the terms and conditions of the SCEE beta test agreement if you're selected. Foul play will get you dishonorably discharged from the trial.