Nothing dramatic, just refining the sculpt, and did a bunch of color variation tests. These are the couple main ideas im leaning towards, and most strongly still into the black/silver/gray theme
I also just decimated everything and chucked it into TB3 to play around with lighting, simple materials, and scene setup
Assuming your using photoshop to save your image, here's what you can try.
When you get to jpeg options, save the quality at a lower value. What can be happening here is that the file size is to big which can cause to make it a smaller size for performance purpose. Quality 8 through 10 should be fine.You shouldn't lose anything. After uploading it, give it some time to process. If this doesn't work comment here again.