A Lokean (or Lokian) is an individual, often who considers themselves to be a Heathen, that venerates and works with Loki, the Norse God of Change and Chaos. A Lokean often views Loki to be a "patron God" of sorts, and thus most of their practice and religion tends to focus on him as the main figure- though they do sometimes work with others from the Norse pantheons. Lokeans actually tend to feel that they are drawn to work with Lokis kin through their experience with Loki. They typically end up working with many of the Rokkr (another pantheon I will discuss later) such as his daughter Hel, son Fenrir, consort Angrboda, wife Sigyn, etc.
This path is often called "The Lokean Path". It's thought to actually be a subset of Asatru, which is the main reconstructionalist religion in general where most Heathens fall under. Asatruars tend to work mainly with the Aesir, as the name implies, and thus are more prone to work with Odin, Freyja, Freyr, Thor, etc. This is debatable, however, because many Lokeans do not associate themselves with Asatru, and view themselves as entirely an entirely different branch of Heathenry (which I will discuss later). Lokeans tend to be very, very devote. They tend to favor personal spirituality, UPG, and close relationships with the deities they work with, mainly Loki, over strictly following the eddas and lore. Lokeans, for some reason, also tend to have the most godspousing occurrences.
Loki is a main figure in the Norse pantheon. He is most frequently described as being the God of Change, Chaos, Ingenuity, Complexity.. and yes, he is in general considered to be the "trickster" God of the pantheon. If you want to spark controversy in the Heathen community, ask about a Heathens opinion on Loki. The views vary widely. Some Heathens view Loki as a kind of Norse Satan, or some kind of evil-being. Some are more moderate, and believe Loki to be the trickster God simply put. Some are very pro-Loki, and believe him to be very misunderstood in his role. And others still do not even consider Loki to be a God.
The disagreement about whether or not he should be considered a "God" comes from his lineage. Both of his parents were Jotun (or giants), and Jotuns are typically not considered to be Gods. However, most of the Aesir and Vanir (the two big pantheons) are made fully of deities that have Jotun blood, as there was ever one true pure-blooded Aesir. Most argue that he is a member of the Aesir, which he is, and thus that makes him one of the Gods. He became part of the Aesir through a blood-oath with Odin, and his marriage to the Goddess Sigyn.
Many Lokeans gather via the internet. They find each other on forums and pages dedicated specifically to them and their practice. This is because Lokeans are still somewhat frowned upon by the rest of the Heathen community, and have not been fully accepted. There are some kindreds which consider themselves Lokeans, but generally these are independent and eclectic kindreds who are not associated with the Troth. While the troth can be considered the 'church' and main 'political force' of Heathenry, they do not welcome Loki at their blots and rituals- thus, many Lokeans have negative feelings about attending any sort of Troth related event. Lokeans are often times single practitioners, who are more eclectic in their path than anything. They don't nessesarily feel the need to join a group, and often will avoid groups to keep politics/fighting away.
From a magickal standpoint, Lokeans are fairly active in their practices. Seidhr, galdr, invocations, blots and sumbels are still all magickal practices Lokeans tend to do. Lokeans also incorporate channelings/horsings, offerings, divination, pathwalking/projection and other things into their practice, when it allows. The Lokablot is the "main" holiday for Lokeans. This is called the Feast of Loki. This is usually held on April 1st (go figure). Usually on this day some minor rites are done, and offerings are given to Loki. Many like to offer him firecrackers, shiny things, and fire- which he is known to be a fan of. They drink in his name, and make oaths to him much like any other blot or sumbel. A feast is held in his honor.