I see that the loading screen is loaded with just the files itself, can it be done with a plist file instead? thanks.

As far as I can tell, to do this you first asynchronously load each png/jpg spritesheet file:
[[CCTextureCache sharedTextureCache] addImageAsync:@"sprites.png" target:self selector:@selector(nodeLoaded:)];

Inside of nodeLoaded you can pass the sheet name and load the corresponding plist using CCSpriteFrameCache:
[[CCSpriteFrameCache sharedSpriteFrameCache] addSpriteFramesWithFile:@"sprites.plist"];

After all is said and done you should have access to sprite frames like usual.