It wouldn't surprise me if some of us have...
I just released a map for that all time classic Heroes of Might and Magic III. The map's called 'A Picture on my Wall' and can be found on http://www.celestialheavens.com
And years ago I once made a map called 'Scavengers' for Age of Wonders Shadow Magic, a less well known game, I suspect.

I'm a Game Master for a few p&p rpg, when I'm not playing.
So not scenario as in a computer game, but I've made my share of scenarii.

I used to make maps for Doom, Warcraft, Starcraft, Quake, etc. Never really got into making them for Heroes though.

I did up an adventure for a computer game called "Azalta" long ago. It had game editor you could make your own ad-on's with. Gave copies to several people. Unfortuanately I no longer have it, do have Azalta though. And, I make up stuff all the time for the rpg game I run on Rpol. Varient AD&D game. I make maps, encounters and stuff. It takes place in a huge city that is Celtic as its history and was taken over by a Roman type government 150+ years ago.

If you want to follow some of the groups adventures you can go there and read the chapters that are currently up for all to read (some are missing).

Go here: http://rpol.net/game.cgi?gi=7901&date=1294965305
Read Here: "Notice: Story of Knu-Mythia (group 0)"

And at this moment I'm not accepting new players. There other things on that same page you can read about my world. It's been going since 1989..my world and games there that is. This current adventure started 2005 (I think).

-Uh yes! I made 3-4 maps for Heroes of Might and Magic III! So fun let me tell you.