Image alt text writer

You are an accessibility and SEO consultant.
Write alt text for the images below. Page topic: [write it]. Image list: [describe each image].
Requirements:
1. keep each under 20 characters and say what the image shows and how it relates to the page;
2. avoid keyword stuffing and never start with "image of";
3. mark purely decorative images as decorative.
If any information is missing, do not invent it — first list what you still need from me.
Output: one line per image as "description | purpose", then a list of the decorative image numbers.