I just looked at all the events that are shown on these forums. First off I want to ask a question. Why do you care about having repeat events now? From what I can see there have been like 5 santa events. Personally I don't think you should care so much about having repeats, but you should care about how they are received. If an event was well liked I see no problem in reusing the idea and maybe changing a few things here and there. For example, I heard that the rifle only event a while ago was fun, I would be more than down for another event like that.
Another thing I want to ask because i'm writing this, why do some events not give a skin? From my point of view it seems dumb not to hand out the temp skins for any event. They make people try harder as both humans and zombies and bring the most dedicated people to the server. It just seems pointless not to hand them out for people who beat the event.
Just another thing I want to add, during events I suggest that you implement a "warmup round" like some maps have even if it doesn't come normally in the map. With the crash bug that keeps happening randomly when maps switch it would suck if you couldn't participate in a round of an event due to an issue that is out of your control.
All of the things above said I've only attended one event which was the most recent one so if I say anything wrong or stupid here correct me.
On to the suggestions:
3rd person event, would have to pick mostly outdoor maps so people can actually see what they are defending. Maps would need speculation but deamin comes to mind as one that might be good and if you allow level 3 then it might bring some people in as lvl 3 hasn't been on GFL for a while. I did see you guys had a 3rd person surf event a long time ago so you can probably use the plugin from that.
rush_b: Personally I would like to see this map be beaten with a team of good humans who are actually trying hard to win while a team of good zombies is trying to kill them. This server only has two wins on this map, one is one where zombies weren't trying that hard and the other was a solo that was gotten by stacking. It would be nice to see a clean win.
rapidfire event of tryhard maps with hard last levels The concept here is to have more maps and admins use the admin rooms to skip to the last level of each map so we get less of the boring first stages and more of the parts that people actually want to play. I was thinking along the lines of 7 maps, I don't think I can think of the right maps but I was thinking along the lines of diddle but maybe not as long.
add onto the idea above: I really think that the idea of admins skipping the map to the last level to get in more maps into an event is a good idea. You could have a set of maybe 5-7 maps and play through the last level of each twice and just switch to the next map whether the map was lost twice, won twice and anything in between. If you play the level twice regardless if you win or lose it keeps the server on schedule to get all the maps played and gives people who got mother zombie in one of rounds a lot less reason to complain because they are guaranteed to be human at least one of the two tries as long as the joined the server on time.
No item event
No nade event
Specific weapon events
These are all nice, I don't think you should worry about being to stale with these, you have so many maps to choose from and there are a bunch of themes you can reuse that haven't been used in over a year such as: surf, rizo, and lotr.
I'm pretty new to the server and have only attended one event so take what I say with a grain of salt.