There are many, many things missing from the wiki, and everyone who edits the wiki regularly (for the English wiki, that number is approximately one, which is one more than it was a few weeks ago) knows about enough of them that we will have our hands full for quite some time.
That said, if you want something to be in the wiki, do one or more of the following, listed in order of preference:
1. Add it yourself. It doesn't have to be done well, or even passably well; in return we ask that you be accepting of whatever modifications we make.
2. Request it on an appropriate wiki page. If your desired change is directly associated with a specific page, write on the talk page. If it's more general, use
http://www.cantr.net/mwiki/index.php/Current_events. Whatever you say will be seen within a day.
3. Post on the forums. While there's no official thread for this, I have used the "Use of the wiki" announcement thread (
http://www.cantr.net/forum/viewtopic.php?t=5856) in the past.