Whenever you enter a new map a loading screen comes up from 3 the games preset images yar? Wouldn't it be nice if you were able to set your own loading screen for everytime someone needs to load and enter the map you've made? Would just be a nice touch, and you can put an edited screenshot from the map there.
Actually, you can do this sort of. All you have to do is find the images in the Textures, open them in Photoshop or something and copy/paste an image over the original texture.
In a nutshell, just overwrite the 'loading' images. (loading0. loading1, loading2...and so on)
I've no idea how you'd set it to show a certain image when you'd go into a certain map.