As for the inspiration. My inspiration also sometimes comes from music (Essence was inspired greatly from DMC3's theme) or art and very rarely from what-if scenarios. Usually what I like to do is transform real-life occurances into stories.

Say the scene where a demon wakes up on the shore to find his girlfriend mauled and dead next to him. He doesn't remember how it happened and feels both sad and... happy about it. He eats her. Tenderly. Turns out later she was a Tamer and had manipulated him into thinking he's serving her out of love.
^ That scene was inspired by my bf hugging me in bed one morning at the seaside and I thought "Ooh, such a heavenly feeling. I wonder what could make it grim and tragic."

The scene where Zi kills a demon in a bar was inspired because I had the misfortune to have to attend one gross bar full of half-naked people and bad music and I had to amuse myself. So I thought, "If I was a vampire, I'd hunt here and no one would notice."

For characters in RP, I usually see what other people have created and try to think of roles I can take to make the story more diverse and the team a stronger and better connected one. And obviously they're always a manifestation of some part of me and some part not-me that I'd like to explore.