Clouds look different depending on the way they are formed. Cumulonimbus clouds are good examples of how changes in elevation can form clouds. They form in the lower part of the troposphere, the atmospheric layer closest to the Earth. Cumulonimbus clouds are a type of cumulus cloud aligned with thunderstorms and heavy rain. They form below 20,000 ft. and are fairly close to the ground. This is why they hold so much moisture. Cumulonimbus clouds are also known as thunderheads for their rare mushroom-like shape.
This is an example of cumulonimbus cloud that has different images in it. When I looked at the picture I immediately saw a duck in the middle of the cloud! Can you see it? Then look on the left side of the picture and you can see a Kipling monkey right there. Amazing huh? It's not easy to see that particular type of cloud.