This is a kind of weird minor bug, first seen yesterday, before upgrading to beta2:
The image URL is https://discorsi.openarchaeology.eu/assets/images/docker-manager-ea64623b074c8ec2b0303bae846e21e6.png and it’s 404.
AI-generated summary
Users are experiencing a broken image issue on the Discourse upgrade page. The image URL is https://[forum-url]/assets/images/docker-manager-ea64623b074c8ec2b0303bae846e21e6.png and is returning a 404 error. Multiple users, including steko, precessor, envieme, and risingskylar, have reported the issue. codinghorror initially couldn’t reproduce the issue, but techAPJ later confirmed it after rebuilding a test instance.
The issue seems to be specific to the HTTPS version of the image URL, as codinghorror mentioned that the HTTP version works fine. downey reported the same issue on a different instance, and DeanMarkTaylor also experienced it.
techAPJ has since fixed the issue and pushed the fix to GitHub: https://github.com/discourse/docker_manager/commit/9b59950c62dde60ec5ddb8d76ef3e7dd7947dc49.
Didn’t see that on the two upgrades I did to beta2 today from different Digital Ocean droplets, so almost certainly specific to your config.
I have had similar problem too.
Hmm can we repro this @techapj?
Can you guys share the path to the image that is broken?
and the image is there, just with another file name:
I am not able to repro this locally or on a test instance.
That’s fine. It will probably go away with an upgrade or a rebuild, but I’m waiting a few days until the new header changes settle down.
FWIW, we have the same issue…
discourse (2016e1c)
docker_manager (549b1d8)
I’m getting the same error now, after updating to latest late yesterday (from a rebuild).
All of the image URLs shared so far that are broken are https (mine included: https://sih.onemadogre.com/assets/images/docker-manager-ea64623b074c8ec2b0303bae846e21e6.png), @codinghorror’s above are http. Coincidence, possibly? Only thing I’ve noticed from this page, though. Nevermind, I see this on my test instance as well, which is not an https link.
The only error I see on my forum is a 404 not found, from the chrome console while on the upgrade page.
I just installed a site clean today, and it also has the broken image. 
Looking for: /assets/images/docker-manager-ea64623b074c8ec2b0303bae846e21e6.png
discourse (1850104)
docker_manager (549b1d8)
Okay, I just performed a rebuild on my test instance and I can repro it now. Added on my list.
Just pushed a fix:
https://github.com/discourse/docker_manager/commit/9b59950c62dde60ec5ddb8d76ef3e7dd7947dc49
And verified that it’s working on my test instance.