Anyways I have noticed in a lot of the early custom maps being released that the endings are usually just a dead end or an out-of-order elevator
Or some cake model just sitting there.
I think it would be better if the ending is one of the two following ideas that you would see as standard practice in the conc mapping community in TFC:
1) You just warp back to the start of the map with a "GJ" message or something like that, so you can play it thru again.
2) A big "fuck around / jump around" place.. you know just some cool place with tons of crap to fling yourself thru/off of all over.. not a puzzle, just a place to mess with the portal physics you know? There would need to be a big message or picture of a cake or something to indicate that this is the ending place, and there is no more after this room / place.
Probably some of you already had these ideas in mind and didn't incoporate them because it is still very early on. I thought I would share them anyway though, in case somebody hadn't 
See you guys around.
Higgs
