It appears this issue is a persistent bug reported by several users since the transition to iOS 26. The "blade of grass" image you are seeing is a default system placeholder that can replace a custom profile picture due to a caching error after a major update. This bug typically occurs when the Settings app fails to refresh its local cache, even though your actual Apple Account photo is correct on Apple's servers. If you tap your name in Settings and see your correct face on the following screen, it confirms the issue is just a display glitch in the main Settings menu.
While Apple has not yet released a specific patch, several community-driven fixes have proven successful. Many users found that the system now pulls your account image specifically from your personal contact card. To check this, go to the Contacts app, tap My Card at the top, and ensure your photo is set there correctly. Additionally, ensuring that Share Name and Photo is toggled on in your Messages settings can force the system to re-sync your profile image across all Apple services.
Another effective method involves forcing a sync through a web browser by signing into icloud.com/settings. Changing your photo there and saving it can often override local device glitches by pushing the update directly from the server to your phone. Finally, keep an eye on software updates; while reports vary for version 26.2, some users found that early versions of the iOS 26 rollout required a follow-up point release to fully resolve display issues.