Have you tried prompting with the word "risograph"? It makes a cool effect.
Prompt: Create a collection of icons representing [a theme], they belong together as a single theme. Put them in a 2x2 grid (no lines). The background is pure white. Make the icons as risograph prints. No text. No color distortion. Vibrant and not faded. Stochastic stippling and sand-like noise pattern within color fills. Each icon has a thick black outline.
The theme in this image was "cute but weird animals (that are real)".