The average jaguar prince is (roughly speaking) a human with a feline head and tail, retractable claws, and tawny (fading to white on the chest) fur decorated with the distinctive black rosette markings of a jaguar. They are typically shorter than the average human - though usually heavier*, with a sleek and muscular build that sacrifices neither strength nor agility. Even the most indolent of jaguar princes maintains a fair degree of personal physical power - a result of generations of biological tinkering.
Of course, given their penchant for tinkering with the very underpinnings of life itself, it should come as no surprise that there are some jaguar princes with more extreme manifestations of their totem - most famously, the jaguar prince Arkaed Rageclaw, who eschewed opposable thumbs and granted himself a fully feline form. Most reserve such extreme alterations for their servants, though, preferring to maintain a personal form that can still operate unassisted in human society. And, of course, even among jaguar princes, those capable of such extreme alterations** are not exactly common - most of them are relatively minor sparks, capable of replicating the works of past masters, but without the skill to make more than trivial changes to an established bloodline.
The typical jaguar prince is also male, though it's not clear if this represents a deliberate choice or an accidental byproduct of some past alteration to the bloodline. Almost all of the exceptions are favored consorts who were granted the jaguar totem; there has been no need to find an appropriate title for a female ruler of the jaguar bloodline in the nearly two hundred years since Chalkon's connection to the nexus.
Interestingly enough, when a girl is born to the bloodline, she's almost always an exceptionally strong spark. This may actually contribute to their rarity - most of the jaguar princes would see such a child as a potential threat.
Typical clothing is a loincloth (usually green), and a profusion of jewelry. Some pieces serve practical purposes - for example, jade and chitin shell bracers and greaves that serve as both limited armor and storage for small tools and bits of useful chemicals, or rings that change colors when exposed to particularly subtle forms of biochemical assault. Other pieces are mostly decorative or status indicators, such as the traditional gold and amber necklaces of office. Most "gemstones" used are pearls or other biological materials; amber is considered the most valuable (especially those containing fossilized creatures; the larger and more complex, the better) - mainly because it's nearly impossible to create artificially. (Which makes artificial amber actually more valuable than natural amber - being able to make the stuff yourself is a definite show of skill and power.)
Even in combat, the jaguar princes don't go in for much more clothing than that; their typical philosophy is that if you got hit at all, well, that was your fault, now wasn't it? Still, armor is perfectly acceptable for warrior servants who aren't expected to be quite as competent - and this trend has greatly accelerated since Oberon's (re)-introduction of firearms to the realm; most Chalkon warriors these days are lower status but heavily armored saurian or insect totems, rather than than the feline totems that used to be preferred.
* They might not, however, be heavier than the average human in a realm filled with automated vehicles and support systems and ready access to junk food.
** Addendum: Technically, the tricky part is not in making such extreme physical changes, but in making them not result in a very dead experimental subject a week or two down the line.