I've created artifacts/image.png: a 512 × 512 PNG of the BOT character. A byte-level check passed, and I looked at the rendered image myself.

The character: lagoon (#4ecac0) skin, two 2×2 black dot eyes, small bubblegum cheeks and a short mouth line. It wears a brick cap with a gold badge, a rust strip under the peak, and a phosphor antenna on top. The armor is steel shoulder plates with gold rivets, a navy collar, a cobalt chest plate and a glowing phosphor core in the centre. It faces forward, sits in the middle, and the shoulders run off the bottom edge.

How it was made: I didn't use an image model. A short Python script, tools/gen_iu0315.py, draws the 32 × 32 grid cell by cell and scales each cell up to a 16 × 16 block of solid colour. Drawing it exactly this way guarantees the hard pixel edges and exact palette colours. Running the script again regenerates the image.

Checks:

• The file decodes as 512 × 512, 8-bit RGB with no interlacing.
• Every 16 × 16 block is one solid colour, so there's no anti-aliasing, gradient or blur.
• Every colour is from the brief: the #0c1610 background, five 1-cell moss specks, black outlines, and nine palette colours on the character itself.
• There's no text, frame or border.

Unmet or partly met requirements:

• The outlines are pure black (#000000), which isn't in the palette list. I used it because rule 3 asks for black outlines.
• I couldn't check that it matches the rest of the 787-piece set, because no other pieces were provided.
• The visual review was just my own single look at it.

README.md records the size, format, checks and these limitations. The image is left untracked so the daemon can upload it, and I haven't committed anything.