You know those totems that create a shield and sometimes anti creeper and even those little walkers that create anti creeper and explode when you power it up? is there a way to put them in the editor or use them?
Some of what you describe sounds like it may be CW3, others maybe PF?
Either way, you can extract the images and scripts from a map where you encounter these and then incorporate them into your own map.
Some hints: http://knucklecracker.com/wiki/doku.php?id=crpl:examine_map_resources