I looked in the rules and I don't think you missed any point.
You've got the concept sheet and illustration; format is correct.
character is attacking or defending and we see 80% mini. of the body.
Definitely has country's specifics.
No political/religious signs.
About your image, I believe there is no bad major elements.
The background is a bit confusing with everything that is going on. characters perspective and the buildings don't seem the same for exemple.
I would try again this illustration with a complete different background that constrasts more with the character. Since your country is Mexico, I would give a try with some plants and jungle.
But honestly, this is a great image.
I can feel the amount of work and effort you put in this illustration.
If there were no breaks in the rules and you did great.
Remember that the selection of the judges is also based on their personal tastes.
And sometimes a good work is not picked.
We were more than 320 participants these year, I bet it wasn't easy to choose only 30.
I hope you will get feedbacks about your work and confirmation that you didn't break any rules.