Right now, many events in the Timeline are categorized under the "history" event, including closings, deletions, postings, community-wiki-making, Tweeting, etc:
Now, this would typically work, but "history" is an awfully broad term, and could probably stand some division.
Ideally, moderation actions (like deleting, closing, CWing, merging, et al) could be under their own "mod action" category, sort of like this mockup:
In a similar vein, items like post creation can probably also stand their own "created" entry, similar to how every answer has a Timeline entry. Bounties and the like could probably also fall under their own category, as they're relatively major events in the post history. Things like tweets could probably be under their own "Tweeted" category or similar, but this may be too fine-grained. Given the list provided by Shog in the comments, I've compiled an example list, available over here, which are just my personal ideas for a replacement of the History section.
Would it be possible to implement these changes to make the timeline more verbose?