The files are: druck_radio_7.tga, druck_radio_9.tga, and druck_radio_21.tga
You can drop them in your "..\data\Textures\TNormal\tex" directory and it will overwrite whatever is in the .dat file. You don't really need to recompress these textures back into the .dat (its not like it will help GWX load any faster :rotfl: )
These are the latest posters I did:
http://www.subsim.com/radioroom/showthread.php?t=100292
You can grab the files from there if you can't find them in a .dat. This particular poster pack uses the bedsheets that came in the faukrum mod. druck_radio_9.tga and druck_radio_21.tga are the same pattern as druck_radio_7.tga. So, copy and paste 7 to make you 9 and 21 files and you will have all 3 files that will update your radio rooms.