Thanks, Akka!
Zaela, I noticed that I could put non-dds images in as long as they were named the same, but the client doesn't appear to create mipmaps for them, so they get really nastily pixellated at angles. Floors were especially bad, because they're -always- seen at angles, never head-on.
I made it an option in this app to turn off auto-dds conversion with mipmaps, but I don't see why anyone would turn it off once they see it.
The larger the texture, the less noticeable it will be, but even at 1024x1024, it's still bad, especially when moving.
(Watch at 1080p, of course, to avoid mpeg artifacting.)
1024x1024 ground as a PNG (no mipmaps, flicker flicker flicker):
https://www.youtube.com/watch?v=b9E7zcLiGbU
1024x1024 ground as a DDS with mipmaps (less sharp, but not flickering):
https://www.youtube.com/watch?v=5lIzF2LooMQ