Regarding the current challenge, we're looking for quality over quantity.
I've came up with a small list for anyone struggling for ideas: Base your game on a simple arcade game, maybe Pong or Breakout. Build the basis of game first, and then see what you can add to it to make it more fun.

Take a look at certain free 1-bit assets. The challenge is a maximum of 3 colours (including black), so you don't have to use 3 colours. Think about these assets and how you could use them. Look at any existing prototypes you've made and see if you can work with one of them.

Finally, if you're struggling for ideas for graphics, sounds and other assets, take a look at https://kenney.nl/, https://itch.io/game-assets/free, and https://opengameart.org/. All Kenney's assets are CC0, meaning you can use them for whatever, but please make sure you check the licence of any assets you find on itch.io or OpenGameArt.

Remember: Quality, not quantity. I'd rather have 1 level of a bug-free and polished game than 100 levels of a game that struggles to run.

Hope this helps!

-Nat