suggestions welcome

Done.

Btw, how can we put these in Flathub and Snapcraft?

For flathub (and probably snap store as well), you only need to update the appstream metadata. As soon as a new version is released to flathub which includes this changes, the screenshots will be automatically updated.

In T12298#212614, @jbbgameich wrote:

For flathub (and probably snap store as well), you only need to update the appstream metadata. As soon as a new version is released to flathub which includes this changes, the screenshots will be automatically updated.

Thanks, pinging @ognarb, iirc he had proposed to do this.

Cheers