Hi Maxwell, welcome to the forums.
The old Warhammer mod is not compatible with BTS 3.19.
The current Warhammer Heart of Chaos version *is* compatible with BTS 3.19.
However, it is a pre-alpha build, and still has many bugs and many many missing features.
Scenarios definitely don't work, but with 3.19 you should be able to load the heart of chaos mod, and then start a random map using some mapscripts (I recommend inland sea).
If this doesn't work for you, then we'd appreciate if you could describe in detail what happens, and what the bug is.
Thanks!