Well as long as I've loved lego, I can also remember a childhood interest in medieval and sword based history. The topography of Ireland (especially my native Ulster) also evokes the rugged feel of living in some epic, with larger than life characters... The endless rain and mist contrasting with the bright and deep greens just add to this effect.
Dunluce Castle (supposedly a great influence on C.S. Lewis and his fiction):
The Giant's Causeway:
And numerous tower houses scattered across the island. I have always loved story telling, and tales, and history always seems a much greater stage than the present or future to my mind.
A trip to see Bodiam Castle while still young cemented my love. One of the most undamaged castles in europe (it claims to be among the last built) and pre-health and safety they used to allow you to run wild throughout. Many a dream project probably dates back to that taster course for the imagination..
I do plan every model quite extensively, though not in the way many others online seem to.
First I begin with a concept normally based on a story or emotion tied to this particular location in some way. At the end of the project I hope for that motivator to still be visible. Then I begin building mentally, starting with key elements and difficult portions. Though still not in Lego form. After this I sketch the complete design, sometimes from several angles, but I'm such a terrible fine artist, friends joke that it could be anything. Finally I build, but very rarely does it deviate from the mental plan. Often a model looks almost identical to the mental version, though almost always slightly inferior ;-)
The source of inspiration is a much harder question. I think God inspires everyone in different ways through different experiences and pleasures, mine normally relates to a story of some kind, or occasionally a particular series of scenic features....
He has at least two posts, though I did coax him ;-)
Thanks for asking and God Bless,
Nathan