First rule of extending the life of a game is multiplayer. The second is providing tools so players can create their own content.
If you'd like to head over to the Internode Games Network, you can download WicEd, a map editor for Massive's RTS World in Conflict. Seeing as WiC had multiplayer from the get go, this utility is for those who wish to follow up on that second rule.
Be warned, it's a chunky 350MB, so start your horses now and unclog those poker chips from your Internet tubes. There's also a 7MB hotfix for the editor, which was just released today.
World in Conflict Patched to 0003 - With New Map, and map making tool [Internode Games Network]