THis is a little reference sheet I've made with all the unicorn species that are in the MW Zone (all of them are in anthro and biped too) and their sizes compared with a human (6' or so)

First one, the smallest and rarest is the City unicorn, they can be invisible to human eyes, although children can see them.
Second one, the Scottish valley unicorn, is smaller than the average valley ones, also shaggier.
Third one, the Forest unicorn (like Senle), can camuflage theirselves with the vegetation.
Four one, Desert unicorn, their hooves are special for not sinking in the sand, called "the golden unicorn" because their fur reflects the sand and made them shine like gold.
Five one, the Valley unicorn (like Aiqi), the best know unicorn, usually pictured in medieval art, are really fast and strong.
Six one, the Nepal mountain unicorn (like Charlie), is smaller than the average mountain, and lives in the mountains the same than in the valleys of Nepal.
And the last one, the Mountain unicorn (like Tietar), also named "the gigant unicorn" because of their size.

Full view is best ^^