We have already logged an enhancement ticket PDFNET-40894 in our issue tracking system for support to delete Images found in ImagePlacementAbsorber. I have also linked this forum thread with enhancement ticket. You will be notified as soon the enhancement is implemented.
I have logged another enhancement ticket PDFNET-42522 for replace image using ImagePlacementAbsorber in our issue tracking system. We will further look into the details of this enhancement and will keep you updated on the status of this enhancement. Please be patient and spare us little time. We are sorry for the inconvenience.