ALERT !!

As of 2.1.0 WoW will now automatically save your screen shots as .jpg, i.e. JPG format. This will cut down size immensely, but it will also cut out some details due to JPG being a lossy format. I've heard a lot of people requesting if it's possible to change the format which screen shots are saved in, for those people who want to change the format back to TGA you'll have to do the following (when 2.1.0 is out)

/console screenshotFormat tga
/console screenshotQuality 10

You can also look for the 2 lines in config.wtf:

SET screenshotFormat
SET screenshotQuality

Change them to what you want and start the game.

Both commands are important, the screenshotQuality is set to 3, which makes it look like a JPG, but in TGA format.

So this concludes my guide on how to change to TGA when 2.1.0 hits, and if you want it back to normal you can use these commands:

/console screenshotFormat jpg
/console screenshotQuality 3

Optionally you could could create an add-on utilizing this, using SetCVar ( http://www.wowwiki.com/API_SetCVar )

As a person who does a lot with screen shots -- and who would rather not have her graphic quality bumped down significantly, all I can say is a warm thanks to Fiskerdin on the forums for writing this tip out for us. Now if you'll excuse me, I need to go kill another character and take screen shots of it standing in front of the rez angel.