You can delete a custom image if you no longer need it.
Log on to the ECS console.
In the left-side navigation pane, select Snapshots & Images > Images .
Select a region.
Select the image you want to delete.
The image type must be Custom Image.
In the dialog box, click OK.
Yes, you can Force Delete the image. However, you cannot re-initialize the system disk of the instance after the custom image is deleted.