I've seen this lately. I believe kevin flerlage may have run into this recently. If I recall, I think the problem was that his image went off of the boundaries of the dashboard. I wouldn't think this would cause that problem but changing the size helped. You may also wish to reach out to Tableau Public to report the issue: Contact Us | Tableau Public
Thanks for the response Ken - I'll give it a go resizing the images but some are within the bounds of the dashboard so don't see why they're all affected. Console also says it's a 404, but I don't know how that could be the case.
The 'contact us' link doesn't give anywhere to get in touch directly with Tableau dev team, only copyright infringement, community forum links etc.
Sorry, I meant to follow up on this. I spoke with Kevin and he confirmed that this is a larger issue that Tableau Public is looking at.
I believe you can probably send an email directly to firstname.lastname@example.org
Thanks so much Ken, reassuring to some degree to know it's a larger issue.
I have reached them on the email you listed too.
Hopefully it can be resolved soon.