That wasnt entirely clear, but I will extract information:
1.) You open GTKRadient 1.5.0
2.) In the textures box, in there is no folder called Common.
Am I right so far?
In case you wanted to know, the common textures are stored in the data-1.1.0.pk3 (that sorta name) in the Tremulous/Base directory
You may want to check there.
Report back on this, tell us a few more things and we'll see if we can help.
Good luck.