|Will the real Lady Agnew please stand up?|
The artist that posted the copy may have learned a lot by doing it. It might be a good copy, but honestly it's unlikely anyone else will be impressed by your work when they run across it online. No matter how good it is, it will never match the original.
So if you must share your master copies on the Internet, may I suggest the following practices:
1. Add a black border around the image area and write "COPY of [original artist + title] by [your name]." under the image.
2. Title the file name in the same way.
3. OR put the original adjacent to your copy and label it below. That way we can see immediately how the two compare, and no one will mind you posting it.