If you give the helmet 'fire damage on self 0 damage' it would set the player on fire and be rather funny, but won't really be a flaming helmet. You could use a script to move a fire to the helmet, but that would require some rather complex scripting (well, very doable, but I don't know how good you are at scripting) to enable and disable the fire as the player takes the helmet on and off, and move it to the player every frame. It also has limitations, as it wouldn't be visisble in the menu and would probably look pretty rubbish. Therefore I guess the best way to do it would be to add particle effects yourself in blender. Particle effects are probably be (I've never moddled) one of the hardest things to learn, but if you must make a flaming helmet would be the best option.
I'd say this is probably the best place to ask, at least there's nowhere better really.
EDIT: Ooh it's been moved. Whatever you say mods...
Blender is not capable of Exporting Particle Effects -> Only Max is and only If your using Max 6-8 and the CivIV Exporter.
Just Copy/Paste a Beth Particle Effect into a Helm.nif, the Helm must be of the variety that is PRN attached because Particle Effects can not be used in the same nif as a skinned armor.
If you use Mesh Emitter Type P.System you can then set the Helm mesh itself as the Emitter of the particles -> this would look the best overall, but a sphere emitter would be ok as well if you can not find a mesh emitter PS that you like.