Refining the texture
The second part of the shading work was to add sub-surface scattering (SSS) with a front and back scatter layer to make the skin soft and add some depth variation.
Once I was happy with the shader, I made some render tests both close to the frog and further away to see the overall quality of my model and shader.
The trick to get wet-effect eyes was to build a liquid shape around the eyes and assign a water-like shader to it. This added the tiny but very important specular which made the head and eye fit together realistically.