Originally Posted by Vladinator
Could always replace the file itself in the Interface\LFGFrame folder, open the mpq and take a look. 
Replacing it would simply mean making the same folder and file structure in the game folders and the game will load the new textures, no coding needed. Don't worry, files that you shouldn't be able to override won't be loaded by the game anyway, so it's okay to play around a bit.  |
Just so you know, you don't have to open the MPQ any longer. Just add '-console' to the end of your wow shortcut, press the ~ key on the login screen and type in "ExportInterfaceFiles art" into the console.
This will create a folder with all the interface art used by blizzard.
The texture needing replacing or editing would be:
"Interface\LFGFRAME\LFG-Eye.blp"
Edit:
p3lim's approach would definitely be the best approach.