You're never going to achieve true depth by adding graphic elements fore and aft of the profile. If you really want to achieve this end you really need to work on form using light and shade, and lose the line-work,
I believe that this advice has been given before, so as ever, this being your work present it as you see fit. Just don't be surprised when you read the same comments with each new post.
There are numerous examples of what im talking about on this very board.