The way Qi Lin have been described to look has changed over the years as they have been used over and over again in different stories for centuries. My understanding is that they were originally described as having the head of a dragon, body of a horse, dragon-like scales all over or partially covering their body, hooves like a horse, a mane that flows upward/outward like fire (often depicted as fire), deer-like antlers, and a long tail also similar to a dragon. They can also be found with only one antler (or horn), which is why they are sometimes confused with the western unicorn.
Qi Lin are often depicted as bejeweled, or with skin as brilliant as jewels, much like Chinese dragons. Their skin is often coloured cyan, with a finish similiar to a precious metal or gem stone. It is said their auspicious voice sounds like the tinkling of bells, chimes, and the wind.
The ancients referred to males as 麒 (Qí) and females as 麟 (lín), but either way, these auspicious beasts were (and still are) revered as the masters of peace and longevity, and are highly regarded by Chinese people. They are also closely associated with child birth.
Due to their deep cultural connotations, Qi Lins can be found all around China as statues in ancient palaces and public spaces, as ornaments in people's homes, shaped in to various accessories, and more recently, tattooed on people's bodies. People pray to these likenesses for protection and blessing (perhaps not to tattoos!).