I have had a Tyranid force lingering around for some time, and 'recently', got my fiancée into Warhammer as well. For the sake of not rolling over her with a force I'm a veteran with, and to motivate me finishing them, I started to research a paintscheme.
I decided rather than going especially fantasy, I would draw inspiration from real exo-skeletal creatures, and picked the Lobster. First, trying to find an image of an un-cooked lobster on Google is interesting. Second, even searching "marine lobster" engaged rule 34!
Finally I found a series of pictures I liked, and painted up a series of test models:
Finally, I have refined the scheme with my Hive Tyrant, now about half finished: