I'm not sure that would help, I think he used different images every time. The IP blacklist doesn't seem to help, and it's still active - I'm only posting on this site through Tor, and it's really annoying.
The biggest problem is how long the spam stays up. You can't completely prevent spam like that, but you have to get rid of it in a reasonable amount of time.
Sometimes the mods react very fast, but sometimes it stays up for half a day, and that's pretty long.

One possible idea: An automated system where posts that get reported will automatically be hidden to the public and held for review by a moderator. The mods then can either decide to delete them or approve them. There might be some false positives, but as long as nobody abuses the system this could work to get rid of CP as fast as possible, and what gets wrongfully reported would get visible again once a mod approves the post - if that takes half a day it should be less problematic than CP staying up half a day. To prevent abuse there could be some threshold so you would need maybe 3 reports from different IPs for a post to get hidden, I don't know what numbers would work.