Hello :D I'm gonna show you how to swap loading screens from your own.
First : Get a picture
You can skip this task if you already have a raster graphics editor.
2nd : Download Paint.NET & install.(usefull program for editing picture it's lightweight compared to Gimp)
Download Paint.NET - Free Software for Digital Photo Editing
3rd : Open your picture with Paint.NET and resize it to 512X512 pixels, click OK.
Now save it as .png 24bit
4th : Convert your picture with "BLPConverter" drag picture into BlpConverter.exe.
Download Files » Programs » BLP Converter 5
Congratulations your .blp picture is ready for insert into .MPQ!
So now what you need to do is making your patch-x.MPQ
Here are the path :
-----------------Folder------------------\yourpicrenamed.blp
Interface\GLUES\LoadingScreens\LoadScreenEasternKingdom.blp
Interface\GLUES\LoadingScreens\LoadScreenOutland.blp
Interface\GLUES\LoadingScreens\LoadScreenKalimdor.blp
Q: Do I need WoWMEfix ?
A: No you don't.
Voila you are done !