This is a day long task.
Use a page in your notebook to scrapbook.
Take time to find visually stimulating items during the day.
Cut them out of magazines or print them off from your browser.
Paste them into your notebook.
Visual stimulus can be a great way of prompting ideas. Try collecting themically linked items, or simply just anything which jumps out at you. This is great to do with magazines when you’ve reached the end of their life. Think of it as analogue bookmarking.