By Selden
If you can provide a separate cloud texture image, that'd be best, I think: a solid white 32bit png with the shapes of the clouds in its alpha (opacity) channel. Then Celestia can draw the clouds moving across the planet's surface.
The globes are defined using Celestia's SSC planet definition, so all of Celestia's planetary options are available, including atmosphere, specularity, clouds, alternate surface textures, long-lat grid overlay, etc. I just haven't specified any of them.
Ok, I'm not sure I've saved all the cloud files, sadly... But I'm gonna have a look.

That's easy enough, although there's the question of what direction should be "up" and how to indicate it. Currently it's parallel with the surface of the maps.
Excellent news. Well, I've used conventionnal directions (north being at the top of the map).

By JohnVanVliet
there are "river police" HERE,and in the space sim forums I am the "polar / map to a sphere police"
I wasn't aware of that police ! Well, I'm often guilty then ... I confess I rarely bother to do the poles correctly, because they rarely appear on the planetary globes I used in the end.