A command line app to build planet tetures up to level 8, allows more format control than pltex.
Aside from curiosity, this was mostly made to allow use of other DXT formats. It currently supports DXT1, DXT5 (Possibly useless in orbiter, but its there), and uncompressed RGB.
This will allow lowish-res planet addons without compression artifacts. The downside is larger files, and I really wouldn't recommend using RGB for anything over level 7, but its possible.
There is another command line option I forgot to document in the README, to set the 'base' texture resolution, which is by default 256x256. It can be specified with -b<number>. This can increase the resolution of any 'level' in orbiter. The size must be a power of two, but the program does not check. Experiment with this feature at your own risk.
The Python sourcecode is included, and MIT licensed, so anyone is free to extend or use this code in any other project.
***UPDATE***
Fixed a bug with Level 5 textures, and switched to texconv for DXT compression, which is significantly faster. Now uses a modified version of nvcompress (added batch support) for RGB, since texconv RGB files do not seem to work in Orbiter.