Oh my! And I thought mine was creepy...
I really like this idea, this would definitely motivate me, that hat looks really painful! The drawing is really well done, especially that expression, you can almost see the poor elf descending into madness thanks to his Jolly Top. The yellow nails and teeth make it even creepier, it's like he is so run down from all the work that his health is declining. I also like how you put the number on the hat, it gives some perspective on how many elves are working in those conditions, and it makes me wonder how many poor elves have been fitted into a Jolly Top. Hopefully less, now that they have this poster to motivate them >.<
The only other point I can really make is the colouring, I like that you have used so many bright and positive colours for such a dark poster, it exaggerates the need to be Jolly. One thing to maybe improve on is the shading of your colouring? The shading looks like it's mostly gradients, which do work for a cartoony style, it's just that I feel it makes the poster slightly more flat. I do however like the texture on the wreath, it brings a little more detail, which is personally something I visually like ^_^
Anyways, well done, I love how sinister this poster is, and good luck in the competition!