Found out about this mod while cruising around Moddb .
I am not sure if it works with the Black Edition we have here but I thought someone might be interested in it.
Info below:
PK++ Mod for Painkiller
=======================
Date: 15:44 06/04/2005
Site: http://www.pkeuro.com
Contact: mods@pkeuro.com
Version: 1.0.1.64
General Mod Overview
====================
PK++ is a modification for the game Painkiller, specifically made for
tournaments, online, and offine play. The mod consists of the follow .Pak files:
PKPlus.pak
PKPlusData.pak
Fonts.pak
Locs.pak
Waypoints.pak
Mapview.pak
Hitsounds.pak
Which are to be located in your \Painkiller\Data\ directory. To start the game
with PK++ loaded, add -lscripts PKPlus.pak in the command line, such that the
game is run:
\Painkiller\Bin\Painkiller.exe -lscripts PKPlus.pak
On running the first time, your game may create some external folders. You may
edit the contents at your own risk.
NOTE: How to run with ASE, QTracker etc. :
Edit your game executable in the application options to run
Painkiller.exe -lscripts pkplus.pak
NOTE: This mod version requires that you have the latest PK version installed.
Running Windows or Linux Dedicated Server
=========================================
Windows:
\Painkiller\Bin\Painkiller.exe -dedicated -config config.ini -lscripts PKPlus.pak
Linux:
Rename the PKPlus.pak to LScripts.pak replacing the original one. Run in the
usual way. The 1.62 PK Linux server is not accepting command lines parameters due
to PCF's oversight, so renaming of PKPlus.pak to LScripts.pak is required.
Steamfish Updater
=================
For Windows client and server versions of the mod, an automatic update utility
has been provided to ensure that you have the latest version of the mod. You can
find this utility in \Painkiller\Data\Updater.exe This will update your mod to
the latest version.
NOTE: Do not run this utility while Painkiller is running, or the update will
not be successful.
Team Recruitment
================
If you would like to join the mod team currently working on PK++ and you think
you have what it takes please contact the ops in IRC: #painkiller.euro @ qnet.
All content of this mod is © www.pkeuro.com. All rights Reserved.
Community Links/Info
====================
http://www.pkeuro.com - Painkiller's #1 community site, features things such as
demos, movies, latest news and much much more.
http://www.thecpl.com - The website of the CPL, the worlds largest E-Sports
event. Also the company running the world tour.
http://www.cplworldtour.com - The CPL World Tour website.
http://www.peoplecanfly.com - Painkiller's developer.
http://www.dreamcatchergames.com - Painkiller's publisher.
Thanks
======
DI-MeisterM for some of the map loading screens.
Id software / OSP for some of the feature ideas.
CPL for their endorsement.
PKEURO.COM for hosting and assistance.
Various testers for their help.
B6 & PrimeviL for their coloured icons.
All the players who've given feedback already.
All other acknowledgements within game.
Contributions
=============
Contributions of Loc files, Waypoint data files, or Mapview images/cfgs are
welcome, and the best ones will be included in later packages.
Feedback
========
For comments, suggestions for enhancements, and bug reports; email
mods@pkeuro.com
--------------------------------------------------------------------------------
URL: http://www.pkeuro.com/files/pk/PKPlusPlusInstaller.exe
link to page: http://www.pkeuro.net/viewurl.php?linkid=550

It sure looks interesting, and I decided to give this a spin, but there's one big problem: the download link available at pkeuro.net's mod page redirects to some shady search page... Seems the mod was removed from the server.
Even on IMDB, they only specify pkeuro.net as the download location.

If I get it right, it somehow enhances multiplayer in some ways.
Also, it adds bot AI to the MP levels, and I'd gladly try that if the mod was available...

Yes, it's supposed to be a CPL sponsored mod for Painkiller. I'll try hunting around and see if I can't find a working link.
OK found a link that works. And the version of the mod is either 1.2.1.64 or 1.31.1.64
http://www.tea51.cba.pl/index.php?site=files&file=6.
The download link is all the way at the bottom of the page.

http://www.gamefront.com/files/files/21155918/PKPlusPlus_1.2.1.64_Installer.exe

The other links don't work, here's a gamefront link.

when installing it has official site link: http://www.pkeuro.net/