I worked this way over the whole of the model's texture, using some alphas of alligator's scales and other animals. The most important thing to remember is to take care that the details don't seem fake.
Examples of the textures used on the head
PolyPaint and textures
To paint the creature's textures I used PolyPaint and one alpha to give color variation to its skin. It's very important to keep this variation and to contrast darker areas in lower parts of the model, so you get more volume in the sculpture.
Using PolyPaint to give color variation and volume
After I finished the PolyPaint, I Unwrapped it and baked Cavity and Displacement maps to use them in the color textures later to get more detail.
Unwrapping and creating maps for the texture
When posing the character it's nice to think about the camera angle and to look for some references. Also, you have to pay attention to the line of action and do some tests. To pose my creature, I used Transpose Master, and used masks and Rotation to pose each part of the model following my references.
Using Transpose Master to give the creature a convincing pose
When I finished the pose I used Decimation Master to export the mesh. I was doing a still image and not an animation, so I didn't need to worry about the final mesh.
Note: Always check the Keep UV option, so you can use your textures.
I used the basic 3-point light concept: key light, fill light and rim light. Then I added some additional lights to light up some of the darker areas. It's always good to get some references either from photographs or other artists' work to help with lighting the scene.
Using the basic 3-point light system to light the scene
The shader I used was the FastSSS2 from V-Ray.
Shader settings for the texture
Rendering and composition
After all these processes, I rendered some passes for the final composition so I could have more control in Photoshop.
Rendering passes to help with the texturing in Photoshop
After that I got some images from the internet so I could use them in my composition. I wanted to create an ambience and not just a studio background.
The most important thing is to keep studying and working, because that way you will see an evolution with each model. Here is my final image:
Tiago Oliveira's website
Tiago's inspiration: Jaemin Kin's art