I find the phrase "solo development" to be an oddity. It may fit in a literal way, but doesn't have to be true in the figurative sense. I mean that nobody is or has to be truly alone in what they do; there's usually some family, friends, or assorted people around us that we draw inspiration from.
It just seems an oddity that, to develop something that we hope others use and enjoy, many or even most of us approach it from a "solitary" perspective. Those who are fortunate to have gainful employment in a successful games-development-house probably know that they have a wealth of experience from colleagues and industry contacts; even those who don't work in a company environment or who go at it on their own, should probably know that it's never a matter of developing in a vacuum.
To round out the post, I guess I'm interested in seeing how it affects you, the reader; perhaps you have an example of a non-traditional or unusual source of inspiration for your project? I'd be curious to know.
I used to work in a command center at a military headquarters in Iraq and Afghanistan. I draw some inspiration from those experiences and am putting some aspects of war management into my game :) Though, one thing needs to be kept in mind: games are supposed to be fun. Managing wars is generally tedious and boring. So, we'll see what makes the final cut...