I wanted to mention when you are designing look at these images. Think about the turtle and the pelican. If you squint your eyes and look at either in the photos you took it is easier to see the turtle as it is dark in the middle of the piece = the turtle and the water right around it is light. The pelican is harder to see as it is very close in color value. The pelican and the background.

Also something that helps make a design show up is to use complementary colors to help off set the desired image. As in this color sample.

Happy Enameling!