S2FM has been in development for a couple of years but always lacked features. A couple of days ago they released the HL:Alyx workshop tools without any documentation.
I spent a couple of hours figuring things out and it turns out Valve pretty much added everything in the last minute.
In the following screenshots you can see improved gloss which is similar to Blender's, new hidden lighting system and Subsurface scattering.
It also has support for HDR skyboxes and so forth. It's gonna take a lot of time until I properly start using S2FM due to no models and graphical glitches. It's also still missing AO which is extremely important as it is the worse version of Raytracing but still can be used to make things look more natural. If you've seen HL Alyx gameplay you'll immediately notice barriers sticking out of the ground due to no AO to blend the edges together.
AO is also important when it comes to futa as the penis is usually attached to the body separately and it helps hide all the seams. Without it, almost every render looks like a badly lit 3D room.
Otherwise it's a great program and I love the new UI and quality of life stuff.
So in short:
S2FM needs ambient occlusion and perhaps a proper function to spawn the hidden lights. The default lights are from SFM which are quite bad for beginners and will pretty much give almost every render a grayish look.
Examples of gray renders:
https://i.imgur.com/dv53gQp.jpg
https://i.imgur.com/1KL5zTs.jpg
Fixed:
https://i.imgur.com/B0wWDg1.png
Also expect a Widowmaker render perhaps?