Xeelee
Stephen Baxter's Xeelee sequence is one of my favourite works of science fiction. Veering wildly from the deeply dark and disturbing to triumphant ecstasy, from the hardest of hard science fiction to the most gloriously batshit insane kind of space opera, it's rarely less than magnificent. I'd love this to get an adaptation (a video game ideally) to bring it to a wider audience, but all I can offer are a handful of the ships from the series which I found most interesting.
Mayflower II
One of the first spaceships we encounter in the series uses the Grand Unified Theory drive. At temperatures and pressures close to those of the Big Bang, the decay of matter releases tremendous amounts of energy. GUT-drives are used much like rockets, requiring a reaction mass or propellant to drive them forward, but vastly more efficient (with an exhaust velocity that's relativistic, if I remember correctly).
One later ship, the Mayflower II, has a particularly tragic story, voyaging for many generations between galaxies after fleeing an Earth descending into a brutal, totalitarian government after overthrowing its alien oppressors. The tale is dark as hell, so bleak that I wanted to improve the living conditions at least a little bit. The basic structure of a GUT ship is a reaction mass connected to the engine, separated from the main habitat by a long boom (much like other spacecraft that generate substantial amounts of radiation). But the sheer size of the ship is staggering, something like three miles in length. I don't think Baxter himself stopped to appreciate just what that means in practise.
So I took a lot of liberties with this one. I drew inspiration more from other GUT-ships described in the series than the particulars of the Mayflower II, tried to show the scale of the ship much more explicitly, and made their main habitat look less depressing. What happens in the story is anyway so thoroughly unpleasant that there just isn't any narrative need to give them harsh living conditions as well !
I also made a simple fly-by animation of the ship :
Spline
Somewhat later we encounter the Spline, a species of space-dwelling creatures that hire themselves out to the highest bidder as living spaceships. This, if I recall correctly, was as a form of job security; quite why a creature that can grow its own hyperdrive and use its own body as a warship needs to find something to do with its spare time is (perhaps rightly) never clearly stated. The motivations of the Spline are largely inscrutable, but I found the concept enthralling. The Spline are largely encountered in the novels as the human antagonists' principle choice of battleship.
Also shown here are the "flitters", basically shuttles. They're not all that clearly described form what I remember, but consist of a small GUT-drive, a habitable sphere, and a large forward crumple zone for dealing with collisions.
Greenship
At around the same time the humans begin employing the Spline as their heavy cruisers, they develop the smaller, mid-range fighters called simply greenships (this militant dystopia being heavy on the utilitarian choice of names). Equipped with GUT-drives for local maneuvering, by now developed to avoid any need for much separation between drive and crew, they also have at least a limited hyperdrive. Each of the three crew (pilot, engineer, and navigator) sits in a bubble which controls an energy weapon. Greenships as a class remain in service for centuries, if not longer, alongside a host of capital ships which I haven't depicted.
Xeelee Nightfighter
Ah, the fabulous Xeelee, owners of the Universe... Remarkably, throughout the whole sequence, little is known for sure about them. Certainly they are baryonic, made of ordinary matter just like us. They were also likely the first such life-forms to evolve, and have manipulated their evolution through time travel. With a hyperdrive of essentially unlimited power, enabling them to fly any distance in arbitrarily short times, they appear to be residents of every galaxy in the observable Universe. In terms of sheer power, they are among the most advanced of all science fiction species, with perhaps only the pseudo-magical Time Lords giving them any real competitor. And yet we never have any clue what they even look like, though there are repeated hints that the Xeelee are their own spaceships (though this seems unlikely given that on rare occasions, a Xeelee Nightfighter can be captured and utilised by the lesser species).
Again I took some liberties with the depiction of the ship. Xeelee Nightfigters move by direct manipulation of spacetime using extendable, sycamore-shaped, spacetime "wings" which can be hundreds of kilometres long. They are largely featureless and jet black. This is tremendously difficult to depict artistically : unless you have a cinema-sized screen to play with, it's going to look extremely boring. And while they do have some central pod suitable for a pilot, descriptions of this are practically absent. So I decided I'd deliberately make something more... Hollywood. I gave the central component stylings based on the Goa'uld ships of Stargate, gave the spacetime wings a more menacing look (inspired by the Cylon ships in Battlestar Galactica) and made them considerably smaller.
I made an animation of Nightfighter entering hyperspace. Again I rather Hollywood-ised this, though the wings are described in the books as extendable and "beating".
Many of the above Xeelee ships are also shown in the first minute of the following demo reel. Annoyingly, YouTube muted the audio, which was supposed to be Hans Zimmer's music from Inception, and without this much of the drama is lost. It also shows some of the "Riding the Rock" panorama, which depicts a battle between the humans and Xeelee near the galactic centre. This was developed for the old QuickTime viewer; like the other such panoramas (for the 2001 and War of the Worlds projects) I don't know if there's anything capable of showing it any more, but you can download the file here.