When you say thematic planet names, what sort of thing do you consider thematic or non-thematic?
I'm guessing that calling the planet "Mr Leet's Awesome Planet" is likely to get the non-thematic label, while "New Murdoch" is probably a fairly safe thematic, but whereabouts is the dividing line?
Honestly it's one of those "we know it when we see it" things. It's super hard to generalize about creative content like that. I can tell you that if we think something is unthematic, we'll work with you and let you know.
To some extent: if you think it's thematic, you're probably right. If you're not sure if it's thematic or not, then feel free to run it by us. We don't bite.
Mainly the question to ask yourself is: "If I saw this planet name in one of my games, would I go 'somebody was goofing off with their planet name reward?'" If the answer is yes, then that's probably not thematic.
But there's a whole range of planet names where you might think "oh what a cool name!" and it's still thematic. I can't think of the best examples right now, but something like "The Restaraunt At the end of the Universe" is pretty cool obviously, though copyrighted and only slightly relevant. "Bob's Hole Of Murder" is probably not the best, but "Lord Tarkin's Murderhole" is probably okay or close. I dunno, that's a toughie. "Murderhole" and "Pit" and the like would be easily something that fit.