Roll 'em
Assign an idea to each of the sides of a die. If you're stuck for ideas, you could start with: drawing/doodle, lists, a memory, a review, a quote or lyric, a plan or desire for the future, a photograph, a random object from the location you're in, something from childhood, a current frustration/happiness.
If you're using a bigger die, add more ideas.
Each day, roll the die and create something - either art or writing or image-related - about what comes up after the roll.
You could add a second die to roll to further gamify what you do, adding categories like memories, goals, childhood, or whatever you like.