If you have made your loadscreen & ran it with your map, you will have noticed that it stretches out & cuts off the sides when loading the game.. If you know the basics of photoshop, this is a very easy fix..
1, Open your picture that is to be your loadscreen in photoshop.
2. Make sure the size of the pic is: 1024x1024
3. Now you want to resize the pic to: 800 x 1024 (this will make the pic look compressed a little)
4. Open a new file (file>new), make the size: 1024x1024 & give it a backround color close to your pics color.
5. Place your resized loadscreen pic "centered" on the new backround.
Now you should have your 1024x1024 loadscreen with the actual pic centered on it. Save as loadscreen_mp_mapname.tga (format = tga). So when the game loads this new pic & stretches it, your pic will fit on the screen & the backround will be the only part cut off...