This is quite tricky…
Normally, I listen to a lot of songs while playing or just relaxing on my bed or in the garden. Depending on the music and the atmosphere, I get different kind of ideas. For example;
When I first listened to this song, I couldn’t help but imagine the MC of my current story being in some kind of dark place, secrets and other things just waiting to be found inside it. A hidden cave full of dangers and also treasures? A destroyed lab with secrets just waiting to be found?
And then it happens that somehow they are encountering someone or something, either fleeing or fighting depending on the situation.
But songs are not the only thing giving my mind something to do. My dreams help me a lot as well. One time, I dreamed of myself being some kind of bystander, a third person, so to say. I followed a man through the vast plane of a city unlike our own, until a murder happened. Hearbroken, the man tries to fix what happened and tries to rewind time, but lands somewhere a bit too far. He encounters all kinds of people and in the end, all of his choices lead to the fact that he did save the one he wanted to save, but ultimately he payed a high price for his choices; his own life in exchange for that he loved.
This is partly some side project I wrote down next to FAWR and SC xP
And of course, don’t forget the movies! I see a scene I like, but the outcome is different than expected at first? No problem, for I imagine my own way for how the movie could go. I change the setting, change the thing that the scene was all about, but in the end, the main actions are pretty much similar and yet not the same. It’s fun, but stressing to do as you would need a way to make it fit 
I could go on and on about books and other things, but I need to find some time to sleep as well xP