So i know nothing of how to do this, so I'm requesting learning material and/or a bit of assistance... Unless of course I get lucky and some has already done it!

So because discord doesn't allow for server specific user icons, i get into situations where i forget what another player is or looks like and i feel it would be more immersive if a small picture of their charecter accompanied each post just like the regular user icon does.

Is there a way to use a bot to recognize individual user posts and to add the picture in to the post?

No expert, but I don’t think that bots can edit other people’s posts. They can only read and post their own things.