Hello Peter,
This is the third time that this issue has come up. In most cases, we've been able to prove that WDS is, in fact, indexing file types that would normally be shown below .bat. For some reason, the file types just aren't showing. I've gone ahead and opened a bug with our development team and this problem doesn't seem to be isolated. I'll report back when I have more information. For now, I'm marking this as answered with a bug.
Thanks for providing your feedback.
Paul Nystrom - MSFT