Thriller Ideas

I have been really inspired by Mr Brooks and would really like to explore doing a psychological thriller. I find the idea of having an alter-ego as a character in the film really interesting and would like to try this in the opening sequence of our thriller. I imagine the setting to be a place where the target audience usually feels safe and comfortable but create a twist by making this location scary and dark. I think a park or another family or friends based location. The main character or victim would be someone unconventional so not a typical blond white innocent women who screams a lot. In Mr Brooks the victims were different and yet it really worked in the film and made it more interesting for the audience. I would like a character that an audience wouldn't think would be a victim, someone unexpected.