I find photos phenomenally helpful in helping me conjure up images, particularly of what my fictional world looks like. Having got those images in my head, I can then write about them confidently because I know what I am "seeing" internally.
Reading widely across genre, as well as being marvellous entertainment and educational a lot of the time, also helps me discover other writers' characters and worlds. I can then analyse them as to what I like about them and why and use that knowledge to help me add greater depth to my "people" and my world.
Proverbs can be a great source of themes and titles for stories but can also be used to conjure up images. For example, what kind of character would need to be told to "look before you leap"? The kind of character you're unlikely to put in charge of a fine porcelain collection (unless of course you want the comic effect).
Occasionally things like recipes can trigger images ideas. These make me think about what people would eat in my creative world and I can then devlop those ideas further.