UCP is not an image registry. DTR is the enterprise private registry in Docker Enterprise, but you can manage the images that are in the Docker cache on each node, using UCP. In the images view, UCP shows you which images have been pulled on the cluster nodes, and it also allows you to pull images, which get downloaded onto every node:

Docker images are compressed for distribution, and the Docker engine decompresses the layers when you pull an image. There are OS-specific optimizations to start containers as soon as the pull completes, which is why you can't pull Windows images on Linux hosts, or vice versa. UCP will try to pull the image on every host, but if some fail because of an OS mismatch, it will continue with the remaining nodes. You will see errors if there is a mismatch:

In the image view, you can drill down and see the details of an image, including the history of the layers, the health check, any environment variables, and the exposed ports. The basic details also show you the OS platform of the image, the virtual size, and the date on which it was created:

In UCP, you can also remove images from the cluster. You may have a policy of retaining just the current and previous image versions on the cluster to allow rollback. Other images can be safely removed from the Docker Enterprise nodes, leaving all previous image versions in DTR so they can be pulled if needed.