I receive a lot of story ideas, for events serious and frivolous. I'm always happy to pass them along to the newsroom for consideration. Many good stories have been originally pitched by readers at my lines.
When you'd like an editor to consider assigning a reporter or photographer to your event, I'd strongly suggest planning a bit ahead. Two weeks' advance notice is generally the best bet. I can't count the number of times I've received what would normally be an interesting suggestion just an hour or so before an event is set to begin, and sometimes even as it's underway. If the story is more of a feature than hard news, it would have to be pretty spectacular to mobilize coverage on such short notice.
I also sometimes get suggestions to cover events that have already happened. In fact, I've had two such requests this week so far. In those cases, it's possible an editor might run a photo submitted by a participant, but that's just not the kind of news that most papers generally look for.
And while I can always forward anything on to the newsroom, I'd encourage organizers to reach out to the relevant reporter directly in advance. The newsroom directory is here.