For a while I've been thinking about trying to do some aliens based on crustaceans. This is a tricky prospect as you really run the risk of making something that looks like another big alien or some sort of rubber suit B movie menace.
My approach was to try to create something along the lines of a shrimp with a flexible body, multiple legs and several sets of manipulating limbs. The end result was a bit less than planned as I found that all the limbs I had planned tended to get in the way and leave little room for technology. I also decided to make the legs meaty, with the joints and segments very robust and distinct to keep them from looking like spindly legged insectoid aliens.
Another thing I decided to do was to try to make the details of the legs in relief against a solid core to the figure. The objective was to try to reduce or do away with the negative space underneath the aliens so as to lend a little ease to any casting that might come from them.
I'm still experimenting with animation in the figures and also how to get gear and weapons in there with all those arms and legs.