Why did you choose hammer if you have a supposed lack of creativity. You have a brain, thus you have a subconcious, thus you have the dreams and the imagination you need.
Reality is an illusion, in our minds we can take what we know to be true, and mix it with other things that we believe to be true. We can control our environment.
The map you make has to come from your own story. Work with something simple, avoid water and puzzles involving it as you arn't going to create anything worth looking at. Make sure you have ep2 and using that engine to make the map in as you then have the benefits it brings (more props etc).
You can drop me a line on steam if you like. skeeter423. I am an oldschool games tester and newschool games designer :)
Oh, and read my blog, it might get the neutrons whirring.
http://darkironphoenix.blogspot.com/