I am currently replaying Doom 3 because I was in the mood for a nice horror shooter. I have installed the "Absolute HD" mod, which is a combination of Sikkmod and some highres textures. The mod features Parallax occlusion mapping, multiple SSAO algorithms, some nice post effects and soft shadows. The latter are horribly slow depending on scene complexity, so I had to disable them (GTX 1070). The end result looks amazin regardless (especially the HBAO), although there are some graphical glitches every now and then. Here are some screenshots!
Apparently the Absolute HD mod also has some gameplay changes, which I did not care for. I wanted pretty much the original gameplay, so it's a good thing, there is also a "Gameplay fix" available for Absolute HD, which reverts most gameplay changes.
Lastly, I installed Open AL Soft, which we use in TDM as well by now, to get the nice HRTF 3D audio. This is really amazing in Doom 3!!! I love it!