Opportunity's final message home is not much to look at on its own. If you're old enough to remember film cameras, it looks like the final exposure on a roll of film, but still missing. It's a suitable epitaph for Opportunity's mission.
Opportunity captured this image with the PanCam, or Panoramic Camera. The rover has the solar filter at the time, which is why the image is so dark.
It bears similarity to Opportunity's first image from Mars, so taken with the left Panoramic Camera.
Martian Sol, in the Perseverance Valley. It was captured at about 9:30 a.m. PDT (12:30 pm EDT) on June 10, 2018, one year ago today. It's the image of the Mars Reconnaissance Orbiter at 9:45, then on to Earth. It arrived here at about 10:05 a.m. PDT (1:05 p.m. EDT), where it was received by NASA's Deep Space Network.
The image is dark because the Sun is blanked out by the global dust storm that envelops Mars at the time. The graininess is camera noise. The black area at the bottom represents the data that was never received. Opportunity's before it could send the rest.
It's not the final image from Opportunity, but it's the final full-frame image. The rover sent thumb-nails from other images, but none of the full images were sent before.
Over the course of its mission on Mars, Opportunity took over 228,000 images. You can see them all at NASA's Opportunity: All 228,771 Raw Images. That's an un-curated collection though.
For a curated gallery, visit Mars Exploration Rover Images.
To browse a collection of panoramas, visit Mars Exploration Rovers Panoramas.
RIP Opportunity. Gone but not forgotten.