Here's another thing that I've had lying on my desk for a very long time.
Ages ago, I bought a skaven abomination. With the help of a lot of DAS clay and a Tyranid head, I made the lower half into a dragon. I was never totally happy with it, and I decided to give it a sprucing-up and repaint to match my pirate ogres. It would make a good sea monster, that they had induced to help them.
I added fins to its body, neck and tail. The body fin came from a high elf dragon, and the other two were left over from some river trolls (which also joined the ogre army). The head received some "ears" from (I think) an ancient plastic dragon kit, and the crest was elongated with plasticard and green stuff. The barnacles on its back were just blobs of sculpted green stuff.
I made the base out of coffee stirrers and a small stick of dowell. There's something weird about painting wood to look like wood, but it works far better that way. I don't have a work in progress picture, but for comparison, here's the GW skaven abomination:
And here's another picture of the sea monster. I gave it quite a dark paint scheme, to suggest something that lives deep underwater. I'm not sure why it's got all those stitches all over it (perhaps a helpful ogre repaired it after a big battle) but it looks mean enough to join the ranks of the pirates. Arrrgh!