Use a Reference Image
You can create any shape you want out of clouds, all you need is a reference image. In this example, we use a bunny photo to define the shape of the clouds. Simply bring a reference image into Photoshop and cut the object out of the Background using the Magic Wand Tool. Once the shape is roughly cut out, it is time to copy clouds over the shape. Make sure to use enough clouds to fill the shape.
To copy clouds, go to ‘select – Color Range’ and click on the white of the clouds. Then create a New Layer and fill the selection with white. This will make a cloud with a Transparent Background that you can move around the image. Duplicate this layer and move it to cover the original shape if needed.
Use a Custom Brush to Define the Edge of Clouds
After covering the original shape with clouds, use a Layer Mask to define the edges of the clouds to fit the edges of the shape. To make the new edges of the clouds look right, use a Brush made from other cloud shapes.