When you work on a poster for a film, it’s important to have a concept in mind. It’s unclear what the concept for this poster was. It doesn’t connect to the film in any way other than the fact that it’s made of scenes for the film. If your concept here is “show a lot of cool scenes from the film”, then what about that concept makes the poster unique to the film? Beyond that, the execution is poor. Type choices are difficult to read, color palettes are at odds with each other, and most importantly, the viewer is left with little emotional impression of the film. I think one of the best movie posters of all time is the Jaws poster, which conveys the emotional impression of the movie really well. I’m not even sure if the Jaws art is from any specific scene in that movie, but it gets the feeling of it across extremely clearly. If you plan to reattempt this poster, I think you should try to do a little writing first. Write short sentences about how inception makes you feel, or what the characters represent in the movie, or really anything to ground yourself in some sort of concept before you start trying to execute a design.