DTM has released a number of new (?) planetary environments in recent days, so I'm going to get to all of them now...
First, the Yavin IV and Mustafar environments have been given re-textures, and you can find screenshots of both environments here
DTM has also released a planetary environment for Bespin, which can be used for just about any high-altitude atmospheric mission. The environment comes with an OPT of Cloud City (the way he chose to do this OPT is pretty clever...you can read how he did it, along with screenshots from Bespin, here
As always, you may download the new environments from MTD Industries