It's hard to know what events are placed because the level is zoomed out so much. Taking screenshots in-game would remedy that (try F12 but make sure you have plus. You can make JCS open plus by default by renaming Jazz2.exe to something like jazz2-.exe and jazz2+.exe to jazz2.exe.).

Anyway, it's very corridory and horizontal. And it looks like the 1 tile passages above the middle would be campy. Whatever is in those cramped looking deadends that are above the tight bottom passage, looks potentially campy as well. Same with those 1 tile passages that lead to the top.

Making an interesting layout is mixing horizontal and vertical spaces and utlising different ways to reach areas (I don't mean as many alternate paths as possible, I simply mean not relying on one method of platforming to reach up areas). Varying the size of spaces allows for more varied gameplay too, and have no need to be parallel, (excessive parallel passages results in a corridory layout which is bland if you ask me). And be sparse on cramped areas, because people will camp in them, and/or it'll get annoying having to get hit by everything. Though 1 tile vertical passages are fine, providing the area above isn't hard to counter.

I'm also not a fan of entirely closing up the top area unless it's inside something man made or a cave.

Though to be honest, I don't recommend making MP levels if you haven't played the gamemode much, if not at all. When you play online (the main MP gamemodes such as battle and CTF) for a good while, you get a much better idea of what works well and what doesn't.