Why don't you browse around the forums first.I'm sure you'd find a lot of interesting additions to the stock engine.
As far as I know
CoZ made a parallax shader for FPS Creator.
The way to add it is :
1.Open the segments folder and find the segment .fps file which you want the shader to be applied to
2.Open the .fps file with notepad and find the values
effect0 = x
3.Download the parallax shader or if you don't want that download
bond1's normal mapping shader from the forums and replace
x with the full path to the shader file (eg. effectbank\ps_3_0\segments\normal_mapping.fx).
You'll also need the shader maps obviously and they have to be in .dds format and be named x_D2.dds(Standard) , x_N.dds (Normal) , x_S.dds(Specular) , x_I.dds(Illumination) , where x is the name of the texture (eg. CrackedWall_D2.dds,CrackedWall_N.dds and so on)
You can also find some mods for the source engine which support deffered shading.
Hope this helps.