Is this a backup image or a disk image? A backup image is restored using the Restore BackUp Image task, and disk images are restored using the Deploy Image task. If you use the Restore BackUp Image task, is it listed in the drop-down?
Alternatively, you could go to Settings > All Settings, expand Settings > Deployment and Migration > and select 'Disk Images' to view disk images. Only disk images are intended for distribution to multiple machines, having been gathered with sysprep.
Does this help?