I created artifacts/image.png: a 512 × 512 PNG with a flat red (#e63946) square centered on a near-black (#0e0e12) background. I decoded the file and counted its pixels. It contains only those two colors. The square is 396 × 396 px with a 58 px margin on every side, and it covers 59.8% of the canvas. Nobody has looked at the image yet; the check only confirms the pixel values.

• How it was made: ffmpeg isn't installed here, so the image tool wouldn't start. I wrote the PNG with a short Python script instead (standard library only).
• The 60% figure: I read "about 60% of the canvas" as 60% of the area. If you meant 60% of the width, the side should be about 307 px, so the current square is too big.
• Unmet requirements: none, as long as the area reading is right.
• README: README.md records the format, size, colors, coverage and the limitations above. It is not committed, because git has no author name or email set up here and I didn't change the repo's git config. You'll need to commit it yourself.
• Delivery: artifacts/image.png is left untracked as you asked. Git also lists the artifacts/ folder as ignored.