Hi, welcome to Vue
Your Lone Tree image has a nice touch to it, good color use and composition. For the clouds there are things you can try to give them more depth. In the Atmosphere editor there is a Clouds tab that will give you controls to play with. Try increasing the clouds density. You can also alter the actual material the cloud is made from in the materials editor. Go to that clouds tab and then edit the material in the lower left. The type of atmosphere you have will effect the controls that are available in the atmo editor. There are loads of  subtle and not so subtle things you can do in there to create lighting and atmospheric effects for your images.