There's a comicinfo.xml metadata in a software called ComicRack. CR is only for windows and no linux program has proper metadata / database handling yet. Perhaps MComix could have this feature.
metadata support allows cbz to behave like mp3's with tags. I can for example just mail a .cbz and the receiver gets all tags from the metadata. Also it allows the program to copy metadatas into a database from witch the user can make advanced queries.