1. in the entity file for your duck you want to have a section under the scripts area that is called initialize (check other entity files for reference).
2. add a new variable to it like "variable.variant = math.random_integer(low, high)" you'll want to make the low end 0 and the high end how many textures you have -1 (so count up from 0, if you have 5 textures you would make the high end 4)
3. in the render controller for your duck add a new array and call it "textures" (again see other render controllers for reference). add all of your textures into that array.
4. under the "textures" object in the render controller outside of the array cahnge it from texture.default to "array.textures[variable.variant]"
that should be all there is to it. you could also check my cod to koi texture pack it has the same principle tho it might have a few more steps.
Hope this helps!
