Some notes on technology.
I'm used to technology levels in GURPS, which are a bit different to those in Traveller, so I've clarified things here for my own use, for what a typical culture of a given tech level would be like. A basic overview is available in the Traveller Wiki, but I'm trying to pull together multiple sources to get a comprehensive list of technology.
Note that I assume that a Tech Level is pretty much what a world can produce or at least maintain itself, not necessarily what is available. A world on a major trade route will tend to have easy access to whatever technology is available on neighbouring worlds, at least for small scale commercial items.
TL 0-2 are pre-industrial revolution. The only technology available will be what comes in from outside.
Civilisation will be tribal, warring kingdoms and the start of massive urbanisation.
3 - Industrial Revolution
Industrial revolution, 19th century Earth. Horse and steam power.
Mechanisation and basic chemistry and medicine, early 20th century. Basic cars, common (but expensive) international travel, air craft and big cities. Telecommunications will be widespread, but not ubiquitous.
6 - Nuclear
Nuclear power, early mechanical computers. Big cities and common air and sea travel. 1950s Earth.
7 - Semiconductors
Basic computer technology, heavy urbanisation and the growth of cities. Late 20th century Earth.
8 - Communications
Early 21st century Earth. Mobile communications are ubiquitous, air travel is cheap. Glass and concrete cities.
9 - Gravitics
The primary indicator of TL 9 is the invention of Gravitics, which allows cheap access to orbit as well as providing a game changer for personal transport. It's often too early for it to have made time to completely impact how cities are designed and built though.
Orbital based industry, commerce and recreation will begin to move into orbit. Sizeable space stations, with some presence on most worlds in the system. If there is a belt, massive mining of that belt will have occurred if the world is high population.
Aircraft are rapidly replaced with grav vehicles, and personal grav vehicles become common towards the end of the period. Most vehicles in a city will still be wheeled however. By now, most vehicles are electric.
Small holographic displays are possible, which will be used for street signs and small advertising boards inside shop windows.
The first jump drives become available. Colonisation of the entire system is possible.
10 (A) - Fusion
Cities are starting to take gravity manipulation into account for large scale planning. Car parks only accessible via the roof will be common. Small scale floating buildings will be possible, powered with their own mini fusion plants.
Cost of power will plummet to allow cheap electricity, so power usage increases dramatically. Many ground vehicles rely on anti-gravity.
Larger free standing holographic images means full window displays, or holographic statues for art of entertainment in plazas. Use of fossil power is almost completely dead, with everything running off electric.
Climate engineering or geoforming becomes common. Space travel is trivial, a lot of heavy industry has moved to orbit and for garden worlds massive mining is done off-world for ecological reasons.
Cybernetics is becoming common and good quality, though still mostly limited to medical reasons.
100% communication coverage on a world is pretty common, unblocked by buildings or terrain.
11 (B) - Fusion+
Availability of cheap power is commonplace, so is rarely a limiting factor. Flying buildings are frequent, if not common.
Cybernetics is commonplace, even for basic enhancement. Augmented limbs or mood enhancement chips are possible.
Large building-sized free standing holograms are possible. Streets are full of holographic advertising, building fronts will tend to display whatever they desire, though they are obviously holographic in nature.
12 (C) - Sophisticated Robots
Cheap power and efficient gravitics means that it's just as easy to build a flying building as it is one sat on the ground. Cities may be a mixture of tower blocks and floater plates carrying whole districts. Realistic looking holograms can be used for advertising or art.
Travel across a world, and into orbit, is trivial and common place. Commuting to orbit (or to ground) on a daily basis is not unusual. Grav belts are easy to obtain, the only thing restricting their use is that it's far more comfortable to sit in an air car.
Cybernetics is reliable, and looks just like the real thing. Skill augmentation is possible, and people will be seen with head jacks for plugging in new skills.
Humanoid robots are becoming practical, though they are obviously robotic in nature. They are more often housed in military or industrial shells rather than true humanoid shells.