Sorry to hear you're struggling with intrusive thoughts. That can be SO hard to control. I like the idea of a collage because it's something visual you can specifically direct your attention to. I would suggest soothing visual images of some kind . . . whether you picture them internally or paste them onto paper as a sort of collage you can look at. How about photographs of mountain streams, beautiful sunsets, baby animals, etc.? Internal visualizations are also good, the guided imagery.