[Nocturnals]

Have you looked at orbiter (http://orbit.medphys.ucl.ac.uk/)?

I know they have some high resolution maps for several planets .

Go to download->optional high-resolution texture download (http://orbit.medphys.ucl.ac.uk/mirrors/orbiter_radio/tex_mir...). I don't know the format so I could be mistaken but I think it also includes elevation maps.

[exDM69]

I know Orbiter and I have been using textures from Celestia add-ons.

They are typically normal rectangular textures with the usual distortion.

Thanks for the pointer.