Preheat oven to 350F and line a 9x13 metal pan with parchment paper.
In a medium bowl, add all-purpose flour, ground cinnamon, baking powder, baking soda, salt, ground nutmeg and ground all-spice. Whisk and set aside.
In a large bowl, add brown and white sugars, vegetable oil, eggs, and milk and whisk well.
Add the dry ingredients into the bowl and mix with a spatula.
Fold in shredded carrots and pecans just until combined and pour batter into prepared baking pan.
Bake for 26-28 minutes or until a toothpick comes out with moist crumbs when inserted into the center.
Allow it to fully cool in the pan before icing, or transfer to a cooling rack/cutting board to ice.
Make your icing by cream cheese and butter the base of a stand mixer and beat until combined and it starts to get lighter.
Add in 2-3 cups of icing sugar to start, along with vanilla extract and salt. Beat again until combined and add in an additional 1-2 cups depending on the consistency and sweetness desired.
Add icing to the cake and spread evenly, or to any desired pattern.
If wanting to do carrot designs, add about 3 tablespoons of icing to 1 bowl and 1 tablespoon in another. Add 2 drops yellow and 1 drop red to mix to make orange. In the green bowl add 1 drop green food coloring and mix to combine.
Place each color into a small plastic bag and cut a small corner then decorate as desired.