This is split from #7602, since the preview experience isn't necessarily directly related to the actual experience of publishing, and to better separate those conversations.
From that issue:
Preview looks like this....

A few ideas could be to have an animation such as here: https://www.wired.com/2013/12/a-sandbox-for-experimenting-with-animated-typography-built-by-a-google-designer/.
This has been talked about in other issues and it's worth creating one here to just focus on this and explore. Along with adding some flourish to this page of engagement also looking at the format. This is pretty flat as an end to the experience. Beyond any animation this screen showed above could do with some iterations itself.
Could perhaps bringing in a better previewing to this all also be wrapped in? Thinking about this in stages may be the best, what can we get in for phase one. Then maybe having a preview modal or something on preview could be brought in later phases. I think it's worth in designs exploring freely then distilling back.
Worth noting that exploring things like having this across all devices is important. What could be created that adapts well?
Things to consider:
The post-preview-button loading screen ("please wait, generating preview") appears when you click on the "Preview" button whilst working on a post. Since this screen will appear for a varying length of time for different users, we may want to consider what we can do to make it interesting or exciting. A fleurishy animation could be one approach, or we could try an empty-state animation to help with perceived loading time.
- Is the primary intent here to improve the perceived loading time, or to add interest to the experience?
Both! Mostly improving perceived loading time but also engaging is good here.
- How much time (range) do we expect this screen to be visible for?
This can vary but usually isn't long at all, it just 'could' be. Also having anything is better than even a flash of white blank screen.
- Do we also need to design for a potential failure? I've seen a few cases (my local install is currently doing this) where the preview screen appears and the post preview never goes away.
This can vary but usually isn't long at all, it just 'could' be. Also having anything is better than even a flash of white blank screen.
- On a technical level, do we have access from this component to the post content or post meta?
This is split from #7602, since the preview experience isn't necessarily directly related to the actual experience of publishing, and to better separate those conversations.
From that issue:
Things to consider:
The post-preview-button loading screen ("please wait, generating preview") appears when you click on the "Preview" button whilst working on a post. Since this screen will appear for a varying length of time for different users, we may want to consider what we can do to make it interesting or exciting. A fleurishy animation could be one approach, or we could try an empty-state animation to help with perceived loading time.