What genre is this? A platformer, an RPG? That may help in creating levels. Other that, here's some things I suggest.
You can create a base level, and build upon that. Of course, if you make one change to the base level, it may change a bunch of other levels. You could also have the elements of a level, and bring them together into a complete level, only saving the configurations. Of course, that could get complicated, too.