Removing duplicate or non-existing images:
1. In the Symantec Management Console, on the Manage menu, click Resource.
2.   In the Select Resource dialog box, select the resource you want to manage,
and then click OK. You will manage (Image Resources).
3. You will see a list of your images that may or may not exist. This needs to be cleaned up.
Option 1:
Do a comparison in the image folder against the image items  listed here and delete each one from the Resource Manager that does not exist.
Option 2:
Make a backup copy of your existing image folder (iC:\Program Files\Altiris\Altiris Agent\Agents\Deployment\Task Handler\image) into a new location and then delete all the images from the original image folder.
Delete all images in the Resource Manager.
Then, go to  the  following folder: C:\Program Files\Altiris\Altiris Agent\Agents\Deployment\Task Handler\Tools and execute the ResourceImportTool.exe. You can now reimport all the images.