Good evening, I have a question. I created a lot of coop maps for portal 2 and each of them are including custom graphics. When I uploaded these maps on steam workshop I thought the custom graphics have also been uploaded. But it seems that I was wrong. If other steam user are playing my maps then they are missing the custom graphics and instead of these graphics they are seeing blank areas. o.O

What could I do to fix that?

I guess you made some custom textures. In this case, you have to pack them inside your BSP map file before publishing the map to your workshop.

You must use a little app called pakrat to do this. There are countless threads about packing custom materials here on TWP, use the search button there's up there at the top of the page

Thank you very much! This was very helpful to fix the problem(s).