@parametriccuriosity,it looks like your image you use to displace with already contains a lot of noise. If it is the one you posted in your original post then the resolution will not be enough to get a high-quality displacement. The best would be if you could find or create a grayscale version of the image. One that doesn’t contain shadowing as the one you posted.
Notice from the topic I linked you to that the images used to displace are all grayscale - black and white really.
So to get the high-quality result you also need high-quality input.
I hope that helps,