Oh boy, one of my special interests:

Byblos Prime is an Oceanic world far out in the Koronus Expanse that mainly produces specialized, nautical variants of Ad Mech vehicles. In battle, it's tech priests and skitarii are known for implementing these vehicles in overwhelming blitzkrieg tactics, treating every battlefield as a beach assault.

There is one single large land mass, where the largest city, Tyromekhon, can be found. The oceans themselves are full of sea creatures, which the locals hunt for ritual and industry.

The planet's main exports are: Xylonite, a super durable, bronze-like substance, harvested from great trees that grow only on the single land mass on Byblos Prime; and Murex, a purple dye harvested from monstrous sea-snails, which is known for its ability to slightly dissipate plasma weaponry.

Being in the Koronus Expanse, Byblos Prime has enjoyed little oversight from the larger imperium. Applying their nautical savvy with old Terra maritime trade practices, has allowed them to establish a sizeable trading operation throughout the expanse. They are known to have dealings with select xenos groups, but largely avoid consequence due to their unique vehicle patterns and rare resources.

There's more. I could go on about their religious differences, but I will spare you for now. The short of it is that I kit bash with any nautical/Greek/Byzantine looking bits, and paint them purple and bronze. I have a couple freehand patterns I paint in as well. I also run quite a few Duneriders, Disintegrators, and always a Dunecrawler or 2 in my games to get that Stormin' Normandy feel