Add names of not found targets to error message in `create_other_body` & add images to docs, readme etc.

[ortk95]

Pull request checklist

• [ ] Add a clear description of the change
• [ ] Add any new tests needed
• [ ] Run spell check on new text visible to user (documentation, GUI etc.)
• [ ] Check any changes to requirements.txt are reflected in setup.py
• [ ] Check code passes CI checks (run run_ci.sh or check GitHub Actions)

See CONTRIBUTING.md for more details.