|I like the idea you are conveying with this, and the overall photography of it is decent. (I reversed it and think I prefer the positive, however) One huge problem, though. There are a ton of JPEG compression artifacts visible in this image, and your filesize of 53k verified that excessive compression was used.
JPG is an image format that can be compressed to make a smaller file. However, it is a lossy format, meaning the compression algorithm looks at adjacent areas of the image and if they are close enough to the same, it codes the data once and simply repeats it. If you compress an image too much, the judgment about what is the same gets really sloppy and you start seeing these grainy, pixelated artifacts.
Always use the least compression you can get away with and still come in under challenge limits. (200k for this advanced challenge) Most image editors have that ability to adjust compression somewhere in the file save dialog. Here is how it works in Paintshop Pro, along with more explanation of compression, if is is of any help: