You can do this as a writing prompt or an art prompt, or combine the two in some intriguing fashion. I snapped a photo of this dinosaur sculpture at Carnegie Library in Pittsburgh, PA a few years ago. Let's use the contrast - the striking rainbow alphabet letters against the gloomy December backdrop of the city - to spark something fun.
Writing prompt: Describe the planet where this dinosaur originated.
Art prompt: Create a page in your journal with a neutral, dark background with one amazing, incredible, surprising pop of color.