Why are some addons working with textures and others are not?
 

The latest beta build yesterday made it so custom textures work. But my own addon won't show the custom textures. Also wowlua won't work with its custom font. And custom sounds still not working.

Is there any fancy thing I need to do to get textures to work. Or did blizzard just flag some popular addons to let them use custom textures?

Maybe .tga hasn't been implemented yet, just .blp.... maybe.

The prat chat copy texture works. And that's a tga file found in \Prat-3.0\textures
After digging around more, its a button. So that may be it only button custom textures are working.

Wowlua button textures work too, didn't think that it was buttons at first.

All my textures are displayed fine without any changes, but I'm not doing anything fancy ;)
Fonts aren't working yet, but you can replace a font you won't ever see ingame and use that for testing (I'm using "Fonts\blei00d.TTF" for example).

Same for me. All textures in DuffedUI works, expect of one. All textures I use are tga-files.