Dark Viewmodels

[Seitan]

Full explanation on the issue here:
http://imgur.com/a/QRKQs

 

[Werewolf]

1) You have env_cubemap's, but you haven't actually built them. Follow this guide - https://tf2maps.net/threads/cubemaps-what-and-how.4530/

2) It's easier for people to reply if you put the text here and use the [ IMG] tags to link to the pictures

 

[MOCOLONI]

1) You have env_cubemap's, but you haven't actually built them. Follow this guide - https://tf2maps.net/threads/cubemaps-what-and-how.4530/

2) It's easier for people to reply if you put the text here and use the [ IMG] tags to link to the pictures

OP is talking about the arms becoming dark inside the tunnel, not the pink textures because of unbuilt cubemaps.

Edit: typo.

 

[Werewolf]

They have the same cause - missing lighting info. On reflective surfaces its the pink/black missing checkerboard, but on surfaces that have all their textures they turn black.