No, but its really easy.

1. Get a picture(s) you want and re-size it to 745 x 350 (You can use a different dimension but that requires overhauling the entire loading screen setup) and save in a .DDS file. Add this file to your mod Textures folder.

2. Edit the loadscreen BRUSHES and WINDOW file in the Window folder. In the former you tell the game what file to look in (the one you just created), the pixel location of the upper left corner, and how far to the right and down the picture lies (also remember to increase the count at the top). In the latter you just add the new brush you made to the list of load screen pictures and increase the count by one. It should be obvious enough just by looking at it, but if you have specific syntax question feel free to ask.

3. Start up the game and you should be good to go.