Thanks! I use Gemini's Imagen 3 API with specific prompts emphasizing "black and white line art, coloring book style, simple clean outlines, no shading".

Key is being very explicit about:

- Line art only, no shading/gradients - Age-appropriate complexity - Theme-specific keywords

Biggest challenge was consistency - took many iterations to dial in the prompts. I also manually filter out images with unwanted shading (working on automating this).

Happy to discuss more if you're exploring similar ideas!