Just recently (within last 2 weeks) set up a private server to hack my screeps code on. Ubuntu 16.04 with MongoDB as per screeps documentation howto page. I did set a password on the server to provide a minimal amount of security.
I quickly noticed my creeps render solid black using the WebGL renderer in the client when connected to my private server. If I remove the password they render properly. Seems the WebGL renderer isn't handling passwords on servers.
Thanks,