A possible way to load large images would be to convert the file to a BMP or similar, strip out the header, and then use a FileStream to read a block of bytes (you'll need the width of the image, which you can get from the header). Then you'd have to turn your bytes into a bitmap. In a windows bitmap, there should be three bytes per pixel, and in the order BGR. Of course, there are a few problems i see. It will probably be quite slow, rather difficult, you'd have to be able to convert the whole image on the fly before using it, again, thats gonna suck up some time, especially with such HUGE images.
My current favourite word is: Bacon!
-SK Genius