You cannot change the past – only move on to the future. No matter what, the sin still happened even if you did full teshuvah and Hashem accepted it. Its a part of your past. I don’t think this is neccesarily a bad thing though.
I don’t think its possible to really erase the image. And I think its there to help us in the future – if you really forget the true, deep guilt that went along with the sin, over time you may forget how bad it is. Then you might sin again.