In fashion, there are collages that are created all the time to express the mood and color way of an inspiration that the designer is influenced by. Its a great reference to use in regards to the design process. Mood boards are created from a poster to using the tools on Photoshop and Illustrator to be expressed digitally. Digital mood boards are clean and professional especially since technology is what we strongly use today. There are many different ways on how mood boards are expressed by creating images that are tiled that are stacked on top of each other, blended in within each image, and any other way the designer prefers.
Here are examples of some fashion and other kinds of collages below: