I mean the image URL of the spam accounts

Indeed, very helpful for the current reply-bot spam. How effective that is will depend on you client. You might also find that muting a word on one client doesn't translate to other clients, too, depending on several factors. I think the OP is just dealing with the npubs that just follow and unfollow people on repeat. Not much to do about those, and I honestly don't notice them, since the clients I generally use don't give me follower notifications. If someone is complaining about it, I can almost guarantee they are using Primal.