Yes, I know, it's a very original idea. The grayscale effect is optional. The effect also makes interactive props freeze in place, which there are few of in Half-Life: Source. Infact I think it's only limited to collapsed catwalks. Anyway, instructions on how to use it are in the readme.
Oh, and the custom models aren't included. They're from the Half-Life: Source - Enhanced mod which I happened to have on my PC.