At this point I have taken a few small spoon shaped scraping tools and lightly carved some muscle tone into the heart, and started carving in some veins. The tool in the photo was made from a piece of a scroll saw blade that was rounded off and sharpened. I used this to remove very small amounts of wax from either side of the vein, creating a raised vein that sticks up above the surface of the heart. I also developed the arteries coming out of the top a little more. I am not trying to make a super realistic looking heart, I think it should be stylized in the same manner as the rest of the piece. I just want it to read as a human heart.