Have you found a solution to your issue?
If not, I would like to know what you expect to see on the two pictures you posted?
How is the image on the front panel incorrect in comparison to what you expect to see?
Could you please tell me the versions number of the software you use for both LabVIEW and NI Vision?
When you create the image refs, you leave an input unconnected. This defaults the image type to U8. Make sure that you connect the U8 output of the 'Image to Array' vis. Also, before you do the subtraction, you should convert the U8 data to I16 to make sure you do not lose the negative numbers. Lastly, make the difference image type 16-bit to visualize the data.