SCREEN 13: i=_IMGLOAD("XD.PNG",256): _IMGPUT ,i

As you say, yours needed ,i on the end. Not specifying the target dimensions/position tells it to stretch/shrink the source to fit the destination(which is screen page 0 by default).

In _IMGLOAD, if 256 is not specified then the image is loaded as a 32-bit RGBA surface, which would have meant the subsequent 32-bit to 8-bit blit would not have worked.

It would only be pretty if the image's colors matched the SCREEN 13 palette.