Mirrors book actually has an entire section on scrying-related mirrors, but it has nothing on how to make them, so it's not very practically useful.

There sure are a lot of types of magic mirror. Mirrors that show you what you ask for or what you need to see; mirrors that you can walk into and explore; mirrors that you can walk through and end up in another location entirely; mirrors that contain bound demons who do various things like warp nearby reality, send messages on command, or scream foul obscenities at anyone they see.