Agreed that the prize should be a cosmetic item, or maybe at a push, a single week's premium-time (all of which cost MC anyway, so it's basically the same thing as giving away MC).
* A unique, Trial by Fire skin (
black with flames like a T-Bird ) would be pretty cool and even though it might be a ballache for the art team to do a variation for every chassis that makes the Trial Mech rotation, would be really good for the player-community, and would draw people in (only one TbF skin per winner in the entire game? Hell yeah).
<New Player in-game>
"How do i get that black skin with the flames?"
<Leet guy>
"Get on the community forums and win the monthly Trial by Fire tournament mate..."
If such a prize was chosen, it would make sense to make a skin for each mech in the Trial rotation, so that the winner receives the skin applicable to his choice of Trial mech (ie; If the winner runs a trial Cat-C1, the skin is applied to Cats, for example).
A simple, black base-skin with flames motif would be pretty easy to knock-up each month for the current crop of tiral mechs as well, so it shouldn't tax the art team too much, if at all.
* A TbF bobblehead would be ok too, and easier to make since the same model could be used in any mech, and it would be more work-efficient to do, since Imho the prize should be utterly unique, not something you can also buy, but
only available by winning TbF, to increase the exclusivity factor & make winning worth something, and to make new players want to become skilled enough to have a chance..
* I'd agree with making it Monthly, gives people chance to learn the trial mechs, and to ensure there's a new rotation each time, plus if a thing occurs too often, you don't look forward to it enough imho.
Also, if you did go with a skin as the prize, it would give the art team enough time to produce a skin for each trial mech to make sure there's a prize-skin available every month, without drawing any significant time from the core work of making content for the rest of the game.