I really enjoyed this article, there are some good tips here

I did some
monster design myself recently for a competition (and won, to my great surprise), though that was designing a wholly new monster which was a bit different - a lot of the process was the same though, it's all about dragging together the different mythologies and sources and welding them together effectively. Even for "new" monsters, you need that background to root it in the real world and make it effective I think.
I should also plug the podcast that organised the aforementioned competition, James Holloway's Monster Man (
http://monsterman.libsyn.com/) which is a really good expanded source on ideas for how to use monsters in games and what their roots are, I'm enjoying it a lot! I may try looking through your versions, too - my German is pretty rubbish, but it might be a good way to improve it a bit (and given I now live in Vienna I really ought to work on it more...)