Because you've loaded the image to the display (bitmap 0), the original bitmap
data will be permanently changed (or in this case lost) by setting the fade value to
zero initially. Like Xenocythe said, load the image into another bitmap buffer (1)
and copy the bitmap to the current display then perform the fade operation. This way
the original image stays intact in memory.
sync rate 60
set display mode 800,600,32
load bitmap "neo games presenta.jpg",1
for i=0 to 100
copy bitmap 1,0
fade bitmap 0,i
sync
next i
wait key
Of course there are other ways you could use to get around back buffering...