Quick swap - exchange .blend files with other participants partway through
Free session
Combine - make something that expresses 4 prompts at once (use the random prompt generator if you need)
Collaborative scene - everybody makes something for a scene, and then shares .blends so that each participant can make their own scenes from everybody's parts
Revisit an old project
Increasing interval studies - try making the same thing in 30 second, 1 minute, 10 minute, 20 minute studies
Three moods - create a simple scene with primitives and present in different ways to express 3 different moods (try experimenting with lighting, camera framing, texturing, animation, etc.)
Childhood memory - express or explore a childhood memory
Variations on a theme - make N things exploring a single theme (use the prompt generator if you need)
Something nearby - make something that's within arm's reach
Iterate - kitbash or modify a creative commons model made by someone else
Opposite - express an antonym of a theme (use the prompt generator if you need)
You - expresses your name or identity