see https://www.reddit.com/r/linux4noobs/comments/fkbq2c/give_unique_names_to_images_that_are_in_different/

move-images.sh

#!/bin/bash
# unofficial bash strict mode
set -euo pipefail
IFS=$'\n\t'

# this is the target-dir for images
TARGET="all-images"

# find the images (change extension as needed)
IMG=$(find ./ -iname '*.jpg')

echo -e "Here are the images:\n${IMG}\n---" # DEBUG

#find the md files
MDS=$(find ./ -iname '*.md')

echo -e "Here are the md-files:\n${MDS}\n---" # DEBUG

# create target dir if it does not exist
if [ ! -d ${TARGET} ]; then
  mkdir ${TARGET}
fi
  
for IMAGE in ${IMG}; do
  FOLDER=$(dirname ${IMAGE})
  FILE=$(basename ${IMAGE})
  NEWNAME=$(basename "${FOLDER}-${FILE}")
  echo -e "We have '${NEWNAME}' for '${IMAGE}'" # DEBUG
  echo -e "mv ${IMAGE} ./${TARGET}/${NEWNAME}" # DEBUG
  # uncomment the following line to actually move
  # mv ${IMAGE} ./${TARGET}/${NEWNAME}
  for MDFILE in ${MDS}; do
    echo -e "Replacing orig with new in ${MDFILE}\n---" # DEBUG
    # add a -i option to actually do it
    sed -E -e "s#${IMAGE}#./${TARGET}/${NEWNAME}#g" ${MDFILE}
  done
done