This mod is made for SA-MP 0.3d and above, it adds de_dust2 map for multiplayer (cannot convert from CS:S, so used a map from cod4)

Map's original post:
http://forum.i3d.net/modifications-cod4/23829-cod4-map-dust-2-classic.html

The gametype for these maps is DM. When you connect, a dialog will appear to choose weapons, and after if you are bored on the map you can make a vote for another one.

If you can script in SA-MP, you can rewrite the mod to any other gametype, or change the first map that loads when the server starts.