DXT1/5 won't matter if he's got a white background :P
You're definitely putting them in the maps folder too?
You could also try using Wadupdater to add the main textures, and then try it in game (just update the wad, don't unzip it) and then extract with that if it works.
However, last time I tried to create a wad from a folder with Wadupdater, I got a ctd in the middle of the loading bar.
Also, don't update the textures straight into the wad (ie open it with Easywad and then just copy and paste the textures in) because this causes huge graphical glitches for some reason (I know you weren't doing that, but just thought I'd say it as a footnote
)