So, this a concept which personally I see with a lot of visual style an epic to descriptions to be implemented for a creature in a fictional world. Probably you can call this "burning head" or "flaming hair", my point is get something that can look like flames surounding the head (but currently prioritized to neck), this can be and usually is applied both to humanoids and fantastic animals. So for lack of a better term, just look for images that represent what I mean even if the explicit concept was not the same.
But first of all some examples of what I mean:
I know probably this drawing tries to represent something more like a spirit than living humanoid which is set on fire "all" the time, but imagine the second option, you could see that flames around the helmet comes from the neck.
Probably this represents a magic energy , but I thougth coould be interesting consider different colors (and maybe temperatures) for this "burning neck".
(Sorry if are too much examples based on pokemon but I have already explained the reason)
Now, passing to the problem, initially we can consider this the common problem of dragons and phoenixes, but just partially based on that personally the problem of a living organisms producing fire have a lot of answers giving possible solutions and others resalting problems are too much (like here dragon that breaths napalm or here in the Anatomically Correct Phoenix.
So, we gonna supose an organism that have the capacity to produce an oil like substance in some part of its body and can light it on using a catalizer or an electrical like eel cell (with a spark), but the problem now is, how this creature could resists its own fire? Till where I know neither a tardigrade could resist this high temperature.
Then, speaking about the possition of "the burning structures", no one creature would want a dangerous fire so near to important organs of its face, eyes can be easily hurt severaly damaging the vision and the nose will breath constant smoke, unless be a complete combustion but now would be stealing the oxygen, and do not forgetting the skin bones and brain. If we have the solution of how this creature produces and resists its fire, would be needed solve the existance of this mechanisms, maybe could be a sexual ornament, with some practical applications that evolved later, like scare predators or generate light during little periods (by pulsant lights), maybe can set on fire its head at critical moments during fights for look imposing or hurt the attacker when tries to hit or bite its head. But whatever the cost-benefit looks uneven. What could be the real uses for this mechanism?
So, I thought is inevitable that we are getting a highly specialized organism, so, my current possible solution is a reptiloid organims, with hard scales (even integrating novel materials, silicon, graphene or iron) from the collarbone joint to all the head, with oil glandules comprimed between the scales, with the lighter structure over the place in which is the pharynx. Still existing a lot of problems, so there are less interesting and focused options, for example just a klamidosaurus collar which looks like fire andd get warm by a high concentration of veins, or just an abundant fur or plumage, that looks fire caused by the color and recovered with an irritating oil that can generate rashes like burns.
What could be your soltions for this?
Edit: I totally forgot how this creature will turn off its fire.