I might have a use for one of those ork buildings. It would be representing a squiggoth breeding ranch, so one of the food buildings or the shaman's hut would be most appropriate. I'm not sure if I can make it fit in the tech tree, though. I also like the look of the firestarter building as an ork radar tower, but I don't think worker tasks can have culture- or era-differentiated graphics. Here's some fluff text I found on Imperial architecture that might help flesh out the Imperial building list. It's long, so I'll put it behind spoiler tags: Spoiler : ADMINISTRATUM The complex organization of the Adeptus Ministratum, or Administratum, is responsible for the administration of the whole of the Imperium; it manages over a million inhabited worlds. Planetary government buildings, records offices, taxation centers, and many more are controlled by the Administratum; they are usually distinguished by the sign of the Imperial eagle over the main door. Many bloody assaults and valiant defenses have take place in and around urban and planetary government buildings; they are natural command posts, and the fall of the Administratum normally indicates the fall of the city. This building is often the attacker's primary target. AUDITORIUM Most Imperial cities have at least one auditorium, where the local populace assemble at great rallies organized by the Administratum and the Inquisition. A visiting dignitary, such as an Inquisitor or a Space Marine commander, will often be requested to lead such a ralley. It is common practice to use the main auditorium - if it still stands - to announce the 'liberation' of a city by one side or the other. CASTRA EXERCITUS According to the provisions of the Codex Exercitus, every Imperial world has a duty to raise and maintain its own planetary defense force. Additionally, each city or world forms part of a precinct where Imperial laws are enforced by the Judges of the Adeptus Arbites. One or more barracks will be found in most Imperial cities, providing accommodation, training areas and armories for the forces they house. Much fighting has centered around these strongholds. CHAPEL Chapels are found throughout the Imperium, and this is a typical example from a world of medieval or higher technology. On many worlds which have fallen to the forces of Horus, chapels have been desecrated and torn down; on some Traitor worlds they have even been turned over to the feral-world cults favored by the Warmaster and his followers. In such as case, the Inquisition normally demands the chapel's complete destruction. CELLARION No world is an island within the Imperium; each gains something from the rest of the galaxy, and each must pay its way. The worlds of the Imperium provide foodstuffs, machinery, minerals and many other things according to their resources. Few Imperial cities are without vast warehouse complexes where the goods are collected ready for shipment to other areas and worlds, and where incoming goods are placed ready for distribution. CENSORIUM Countless clerks and officials labor on a million worlds for the Administratum, most of them confined to dark offices in grim, towering administrative blocks. These buildings house vast quantities of information on their worlds; population, economy, levels of production and taxation, resources, industrial and agricultural quotas - the whole of the world is recorded, filed, indexed and updated by an army of bureaucrats. The valuable data in the Censorium can make it a prime target. GENERATORIUM A city or industrial complex requires vast quantities of energy, and power supplies are a favorite target for attacking forces. The nature of a generator will vary from world to world. Fertile planets often use organic or fossil fuels, while fusion grids and plasma reactors are common on industrialized worlds. Solar generators and geothermal energy are also used where local conditions permit. These power sources, and the secrets of their operation, are jealously guarded by the Adeptus Mechanicus. GENETORIUM Most planets in the Imperium maintain a gene-pool of plant and animal species for terraforming, agriculture, resource management and other purposes. Native species are studied with a view to assessing their usefulness elsewhere, and introduced species are bio-engineered to adapt them for use in local conditions. The scientists of the Adeptus Mechanicus who run these establishments also monitor the genetic purity of the planet's population, and cooperate with the Inquisition in their task of rooting out mutation and other undesirable traits. LIBRARIUM During the terrible wars of the Age of Strife, untold quantities of knowledge were lost. And preserving what was left became a holy task shared by the Administratum and the Adeptus Mechanicus. In many of the larger cities of the more advanced Imperial worlds an imposing Librarium building will house thousands of books and records, and make them available to those Imperial servants and citizens whose rank or privilege entitles them to access. MANUFACTORIUM Although much technology was lost during the fifteen centuries of the Age of Strife, the Imperium is by no means technically backward. Industrial complexes across the galaxy produce billions of items, from clothing to plasma bombs. All of these installations are closely controlled by the Administratum and the Adeptus Mechanicus, and it is not uncommon for the workers in a factory to be completely unaware of the end product of their labors. The occupation or destruction a Manufactorium or other industrial complex can deny precious resources to the enemy. MAUSOLEUM For the vast bulk of the citizens of the Imperium, death is not the end of their service to the emperor. They are quickly forgotten by everyone except the record keepers of the Administratum and their bodies are recycled into foodstuffs, fertilizers, and other useful products. More prominent members of society may receive the honor of entombment in an Imperial mausoleum, where the masses may read of their deeds and be inspired by their example. With its halls of entombed heroes, a Mausoleum can become the focus of a fanatical defense, and its destruction can deal a severe blow to the defenders' morale. There are some strong parallels with civ buildings (castra exercitus = barracks, censorium = courthouse, etc.).