Not CALM specific, but I'm continuing to theme calibre plugins and I saw that some of your plugins icons are not themable. It's the same thing that was happening with Job Spy (The path to the user's local resources/images folder in common_utils.py has to be changed).
It's the case with:
- Author Book Count
- Author Book Count Hierarchy
- Consolidate All Library Metadata
- Drop Search Results
- English Noun Frequency
- Library Codes
- Media File Importer
- Multi Column Search
- Quarantine And Scrub
- Zotero Metadata Importer
Nothing urgent, but maybe you can correct it next time you update them?