I've been messing around with Google Maps and have put together a little web app that I thought you guys might enjoy. It lets you fly your ship over real world locations - so now you can see how enormous 40K ships really are.
It only includes the ships from BAttlefleet Koronus (and a couple from Into the Storm) because none of the others have the right kind of picture. And I couldn't put any of the BAttlefleet Gothic ones on because they don't say how bug they are. Still, there's over 20 ships included.
Be sure to check out the size of the Universe-class Mass Conveyer...
Hope you enjoy it.
voidstate