Dang! Just wrote you a nice, thoughtful comment and then lost it! I'll try and recap.
This is a really cool design! I like your idea of making additions to it on a print so that you don't have to alter the original in a way that you may not be satisfied with. I would love to see what it looks like with a fetus inside it, or a solar system! The size of it is impressive, Would never guess it was that big, just from looking at the image. Knowing the dimensions of the original provides a nice added perspective. I really like this piece, even more now that I have looked at it for a while! Would maybe be cool to do a series with various imagery inside the turtle if you had the inspiration for it:) Good work!