is there a pix fix?
(these are jpg's)
Maybe -- combine the files in an image editor, and run a clone tool across questionable areas to merge them more attractively.
It usually seems that I have better results with the png format in Acad than with jpegs. might be advantageous to try converting them.
The other question that comes to mind, is why you would use a separate XREF file to contain the images and nothing but the images? While I see it done, you lose a lot of control and flexibility of the image display (fade, brightness, ect.) And that may be a factor. In the Xref file itself, do you see issues between the images? or do they merge cleanly?