1. Contrast high-tech and low-tech (or high-tech and nature).
2. Use vertical elements.
3. Choose a limited range of appropriate colors.
(1.)
Combining high-tech and low-tech is an important part of many Star Wars movie sets, such as the interiors and exteriors of all the Tatooine buildings, or the Imperial shield generator in the natural setting of the deep woods of Endor's moon. The greater the contrast between these two elements, the better.
If you are making very high-tech buildings, try to set them in natural or low-tech surroundings. Place a gleaming tower in a jungle or in a frozen tundra. Add a few alien hovels off to one side to make a shanty town that grew up next to that Imperial base, or hide the rebel communications center amongst some crumbling alien ruins.
If you are using mostly low-tech buildings, then add some high-tech details to the walls. Take a typical medieval castle section and add a computer panel next to the drawbridge and antennas on the roof. Walls that appear to be made of concrete or massive stones are good choices for buildings that could mix well with high or low-tech surroundings.
(2.)
Another way to make things look "right" is to use a lot of vertical elements. Think about the cliff walls and mesas rising above the Jundland Wastes, the minarets and antennas high above Mos Eisley, or those enormous Endor trees. It's OK to create some horizontal cover pieces for entire squads to hide behind, but to round out that Star Wars look the table needs a few things that are taller than they are wide, like moisture evaporators, antennas, look-out towers, rock spires, and giant tree trunks. Buttresses on the outer walls of buildings can also help fill this role.
(This is a good place to mention a basic rule for buildings for any skirmish-level game: Break up all big flat horizontal walls. At the very least add some visual detail to the wall with a little drainpipe, air vent, or graffiti. I prefer to add several 3D projections such as large pipes, buttresses, or doorways with protruding frames, each feature big enough to shelter one figure behind it. This actually creates some cover where there was a big open space.)
If you create a lot of this sort of vertical-shaped cover, you will find that it can allow for much more dynamic game action. Instead of lining up behind low walls and slugging it out, squads can zig-zag forward towards their objectives, the troops darting between 'vaporators, energy relay pylons, and communication booths.
(3.)
George Lucas made deliberate choices about the colors in the major scenes in the movies. To imitate his style, contrast the colors of the high-tech (white, grey, black, and metallic) with the low-tech (earth tones and greens). When brighter colors appear on hi-tech equipment they are usually used sparingly. Blue, red, or yellow may appear in small stripes or as lettering and numbering, but most of the surface will look monochromatic. New or well-maintained equipment will be gleaming, while weathered pieces will be streaked with rust and oily grime. The earth tones can be used on natural pieces such as rocks and on the low-tech buildings, which tend to blend into their natural environment.
I do use a few store-bought resin pieces, such as some of the free-standing high-tech equipment units made by Armorcast. They fit into my SWMB table because they are predominantly light grey and white, just like the other pieces I have scratch built. I could have chosen a different color, but I still would have stuck to a similar overall palette and used it consistently across the table.
In practice:
Most of my own buildings are inspired by Mos Eisley, so they look like low-tech sand-colored adobe structures. They are heavy looking structures with round domes and thick buttresses. Each has a few grey and metallic high-tech details, such as control panels next to the front doors, pipes running up the back walls, an antenna on the roof, or an evaporator-like machine on the street corner. The dune-like repetition of the low buildings is also punctuated by occasional taller towers and antenna units.
Back to my Star Wars Tabletop Terrain page.