Here is the humble beginnings of my Leviathan Dreadnought. It's obviously very WIP, and it's only mockup stage (I'm not sure about the sarcophagus or front armour - the shoulder pads obviously need some work as well), but the basics are starting to form - I knew it needed to have the front armour rounded, as well as the shin armour, to match my existing Daemon engines - it would look out of place to suddenly have a lot of square edges. I'm also pondering how to do a Grav Flux Bombard - any ideas?
It's only really when you see it in real life, that you appreciate how big this fella is - but I've included a scale shot, so you can get an idea:
