Here's a scratchbuilt sci-fi armoured car I built a few months ago (only just got around to photographing it :P ).
It's made from styrene sheet and assorted spare 1/35 AFV and 1/24 car parts, and is a "freelance" design I created myself - not based on any existing sci-fi universe. It's actually from a sci-fi setting I created for a computer strategy game I've been working on over the last couple of years (the "Infinity") universe.
It's a Talmor "Trailblazer" light armoured reconnaisance/fast attack vehicle, and is about 1/24 in scale. The design is very loosely inspired by the WW2 British Humber LRC (Light Reconnaisance Car). My original design for this vehicle was closer to the LRC, but it more or less "evolved" as I built the model!
It doesn't look too advanced/high-tech, which is intentional - it is meant to be an improvised, lightweight design based on a car chassis, requiring the minimum of materials and technology for the specification.
Construction is of welded aluminium plate with titanium applique armour plates bolted on to give extra protection to the crew and engine, along with a Kevlar-type inner anti-spall layer. The Trailblazer has a crew of 2 (driver and gunner/commander), is powered by a standard mass-produced car/truck fuel cell motor, and is armed with a light autocannon, two light MGs (one operated by the driver), and a manually-loaded, turret-mounted missile launching rail (similar to that on some modern Soviet/Russian AFVs) which can fire either anti-armour or surface-to-air missiles.
The colour scheme matches the terrain of Talmiun (the home planet of the Talmor) which is a mixture of desert, semi-arid and Mediterranean climates. Many vehicles have extra camouflage applied by their crew in brown, black or green (or a mixture of the three).
This is another vehicle I'm working on from the same sci-fi universe/setting. It's an armoured command halftrack, converted from a light tank (like the German WW2 Panzerbefehlswagen I). Unfortunately the wheels/tracks don't show up very well in the photos.
This vehicle will be open-topped, with a commander's seat and communications equipment in the back. It'll also have spaced armour plates on the sides of the vehicle (you can see the support brackets and the unattached plates in the photos), similar to WW2 "Schurzen".
I've many other designs lined up to scratchbuild in the future (some I've already started work on). Most of my designs are heavily influenced by WW2 and post-war AFVs, given a sci-fi twist, rather than being ultra-futuristic hovertanks and similar.
My future projects include a heavy fighter-bomber aircraft/starship, several standard tanks, a superheavy tank somewhat like the Warhammer 40K Baneblade, and an APC/IFV loosely based on the M113 and FV432. Most of these have a basic hull framework already built, but need a lot more work to complete!