I've accepted IU_0006 and written the review to artifacts/review.json. The JSON parses correctly, and the file is left untracked as required.

{"slot":"IU_0006","verdict":"ACCEPT","name":"Visor Mite",
 "scores":{"brief":8,"silhouette":8,"style":10,"originality":7}, ...}

Checked with code:

• File: downloaded to /tmp/candidate.png, outside the repo, and its sha256 matches 62117e26…cb83.
• Grid: the image is a 512×512 RGB PNG. Every one of the 32×32 blocks (16×16 pixels each) is a single flat colour, so it's true nearest-neighbour pixel art with no anti-aliasing, gradients or blur.
• Palette: it uses exactly 7 colours. One is the background #0c1610, which covers about 44% of the image, and one is black #000000 for outlines. The other five are all from the allowed palette: navy #2b3a6b, bone #f2efe6, brick #df523e, steel #8a8f96 and phosphor #39ff6a.

What I saw looking at the image:

• Character: one front-facing, centred bust, with shoulders reaching the bottom edge. Thick black outlines throughout, no text, watermark or border, and no scenery.
• Species and skin: BUG is shown by segmented black and steel antennae on a bone head.
• Eyes: a phosphor-green VISOR.
• Headgear: a brick-red BANDANA, with knot tails trailing to the right.
• Outfit: a navy JACKET with lapels over a bone shirt.

Judgement calls behind the scores: the "bug" reading rests mostly on the antennae; otherwise the face reads like a generic robot or agent. That is why brief and originality are a little lower, at 8 and 7. Style gets 10 because the grid and palette checks are exact. No reject condition applies.