As a general rule, I'd prefer to first spur your own creativity. This will be your opus, after all.
What do you want to see that you haven't seen before?
Focus on an aspect of the characters, world, or story. Is there something like this that you've been dissatisfied with in another work? What was wrong with it? What would be better than it?
You can transform the material as well to better understand it. What if a character was in a TV show, or game, or an opera, or an ancient poem? What would they be like in that circumstance? Does anything from that also work in the prose version you want to write?
You could also try an Oblique Strategy: http://stoney.sb.org/eno/oblique.html
There was a point in my writing when I similarly had trouble moving from setup to the bulk of the plot. Some strategies that worked for me in that instance:
- Write a short prequel.
- Watch, read, consume more.
- Listen to people, try to understand how they live their lives.
- Expand your reference pool. Something trite to one person/genre can be a revelation used differently in another.