Yup, there are many UT2004 lovers here.
There are still some useful 2K4 sites, though you may find the official Epic forums are now the best place to find active modders.
The Killing Floor mod still has a following so you will find those forums are still active.
Chaos UT2004 is also still semi-supported, and may actually get another update soon !
Just like UT99 there is much you can add to the mix, but with 2K4 the bigger mods are always installed in their own folder.
To make all the resources show in your main game, you must add the new path locations of the mod under the normal paths in the UT ini.
It is worth using the 64 bit patch if you can. It will add a working D3D9 renderer.https://yourunreal.wordpress.com/2012/0 ... eal-files/https://yourunreal.wordpress.com/2012/08/17/ut2004/
If you like monsters, you will love UT2004.