You're Big Macintosh looks really good, but I would like to point out that as a human he wouldn't wear a horse harness. A horse harness is used by horses to pull the plow, but Big Mac isn't a horse here.
There are many wonderful and stylish humanized versions out there but yours are just amazing! You've captured every personality♥ I've seen only a few artists that could actually achieve that. Brilliant.
The bottom left two are Caramel (background pony). Which doesn't make much sense, since one's female and the other's male, but there have been three versions of him throughout the season (bulky stallion, normal stallion and female). The bulky stallion version appeared in the old Season 1 opening (I think). The female version appeared in Over a Barrel. Wikipedia describes: A forgetful pony. He lost the grass seeds during Winter Wrap Up more than once. His design was re-used later in Sonic Rainboom as contestant number 12. He also pulled the carriage in The Best Night Ever along with Lucky. His cutie mark is three blue horseshoes. Hope that helps!