Well, mmf2 imports large images without any problems, and actually without hardware acceleration.
As adrix has already pointed out, it's a hardware limitation.
There's isn't a graphics card in the world that has unlimited VRam and bandwidth, and these things need to be taken into consideration.
You can't just throw any amount of data at the hardware and expect it to deal with it every tick.
MMF2 isn't using magic to load the image you talk about.
It's just not using any hardware acceleration, so it's not limited by the hardware.
Resource management is a basic requirement for game programming.
You really should do some research on it.
I'm sure there's plenty of info out there for the beginner.
Maybe someone will post a few links for you.