I seem to recall that you used to be able to rebuild an instance using an older image that you created from snapshot. That option seems to be gone now and I can only select the plain jane images from the Rebuild Instance.
Weird because the option is still there. What exactly are you trying to do? Do you get error messages or just missing the option? Where are you looking for that option? Maybe the snapshot you created is not bootable? This documentation may give you some ideas: https://help.dreamhost.com/hc/en-us/articles/215912778-How-to-launch-an-instance-from-a-DreamCompute-volume
Through the dreamhost UI, you used to be able to rebuild an instance using snapshots you have created. Now it only lists the default plain jane builds. The snapshots are all bootable.