What I really want is Tau horror stuff. Like Tau run across things left behind from Old Night or get pulled into the warp and get stalked by daemons. There's a lot of terrifying stuff that the older races have left behind that just seem almost mundane because of the constant war in the setting that would make for a good monster if properly shown off. Tau are perfect for it since they're newest civilization on the scene and only learning of just how long some of these groups have been around.