Give the clouds some depth by adding self shadowing. Self shadowing causes the fluid to cast shadows on itself using a single internal directional light at -1, -1, -1.

To add self shadowing to the texture density

1. In the Attribute Editor, under the fluidShape1 tab, open the Lighting section.
2. Turn on Self Shadow.

   

   The clouds now have some darker areas on them, giving them some depth.

3. In the Display section, change Boundary Draw to None to hide the container. This gives you a better idea of how the fluid will look before you render it.