This can change in future, though. If you are interested in this feature, please vote for it in the Wish List.
I have mapped an HDD image, but the system doesn't recognize it. What's wrong?
At the moment CallbackDisk can present one partition to the OS and it doesn't handle images or other representations of disks with multiple partitions. In oher words CallbackDisk doesn't understand or parse MBRs, partition tables and similar metainformation. If you have an image with multiple partitions, it's your job to parse them and create several instances of CallbackDisk class (an instance for each partition).