I don't know if hydroponics is a good example; it's use in human agriculture is also rather limited. For the most part, there's really no good reason to use hydroponics on land. In space, it means you don't need to bring a lot of dirt with you, but on a planet like Earth, that's usually not a problem. Hydroponics is currently mainly used in laboratories and for growing dirt-free vegetables, which have a small market.
Also, the Kilrathi do have an appreciation for art. The Kilrathi make a number of highly stylized artifacts, including their ships. Any quick comparison of Confed and Kilrathi ship designs will show which race is portrayed as utilitarian, and which race is portrayed with a sense for the finer things in life.
Also various throne scenes, Kilrathi ornamental armor, etc.
Yes, historically the warlords sought land; like any classic feudal culture, land was the primary measure of wealth. However, towards the end of the shogun period, rice and land steadily became less valuable, and the commercial classes which were so disdained steadily acquired more influence. So maybe that's not such a good example, either. And the novels seem to indicate that Kilrathi nobles had a real interest in acquiring vast amounts of "land"/planetary bodies (as would fit a territorial predator species), so perhaps they share that trait as well.
Now, it's certainly true that the Kilrathi showed no real inclination to copy human ways, so that's certainly a point of difference. They did tend not to invent their own technology, but acquire that of conquered races; still, I think that's a rather minor point.
Now, obviously the Kilrathi are a caricature; it's probably a bit much to expect a highly developed and realistic picture of the Kilrathi culture from the very start with the first Wing Commander game; after all, in the first game the Kilrathi are only seen as pointy-eared aliens in comms and a few cut scenes. And Forstchen's liberal borrowing from WW2 history probably didn't make the Kilrathi-Japanese connection any more subtle. However, I think it's quite obvious that the Kilrathi are clearly a caricature of imperial Japan, especially with respect to the Pacific campaign in WW2.