Hey, I usually don't review triggerless scenarios, but thought it might be helpful to give you some constructive criticism.
The map didn't provide fun gameplay - mostly due to the lack of triggers. Add triggers to set techs, grant god powers, name your centaur, power up animals, and just make the map more fun in general. Be sure to check the bottom of my review for some helpful tutorials on triggers.
Even though you only had to fight animals, there were still some issues with balance. For example, a single centaur cannot go up against packs of wolves, rhinos, bears, walruses, and lions. I'd suggest granting player one a restoration god power for every ten kills, or something like that.
The general idea of the map was fairly creative - just not well created. Add some more creative things - like harder animals to kill, and different bonuses when you kill a certain group of animals. Ideas for the bonuses are granted god powers, techs, improves LOS/Attack/Health. Just play around with triggers and I'm sure you will be able to greatly improve your map.
Map Design: 1
The map design was very bland. For the most part, the terrain was just SnowB. Try mixing some more snow terrains to create a more natural looking environment. The trees were nice but too clumped together and didn't have enough variations. I would suggest adding some tundra trees along with the snow pine trees as they make a great combination. The animals did not seem to fit in. For example, if you are making a snow map, add polar bears, wolves, and caribou, instead of rhinos, lions, monkeys, and zebras. Also, it would be nice if you created small nature add-ons like bushes, rocks, rotting logs, ruins, etc. And perhaps add a different and more unique light set. Take a look at some of the top rated custom scenarios to see examples of great map design.
No story or instructions were given in your scenario. I'd suggest starting by adding an objective telling the player what to do. Also, explain the storyline more. Why did the gods make the centaur's life a misery? Why is the centaur taking his anger out on the animals? I saw you had some unused camera tracks in the editor, that's a good start. Just expand on those cinematics by creating the required triggers and dialog, and that will be a great way to explain the storyline of the scenario.
To improve your scenario, check out these guides: http://aom.heavengames.com/scendesign/
Most importantly, check out this great trigger tutorial: http://aom.heavengames.com/scendesign/advanced/trig1