@bigmacintosh2000  
I actually was about to point that out, you generally draw in the “anatomically correct” direction, except for the teats, you draw them like what’s usually called “crotchboobs” (like on humans), despite them being more like udders on the mares.  
Then again, if that’s how you like it, no problem, it’s your art after all ;D

@SillyFilly  
I’m already following those two artists. I really admire their work.
 
I’ve got a couple of pictures in the pipeline already where I worked from actual pony/horse photos, but put MLP faces/manes/tails on them. In one case I’m really pleased with the result, but in the other there is something to be desired from the reality of it. After doing one or two more of those, I plan to take lessons learned and go back to more stylized pony bodies, but hopefully with improved muscle contour and leg joints. Basically, real mares tend to have these big bellies in an unsatisfying way, and the teats aren’t that nice.

@bigmacintosh2000  
I’m happy to see you using proper references for improving your skills, that’s always a good idea!  
As for lingerie making sense on ponies (or other non-human characters), I suggest looking up ecmajor or longinius, they’re the best in that regard, in my opinion ;D  
But I think, you generally did pretty well there already!

Also, it then occurred to me that 1. lingerie and tack have a lot in common, and 2. country mares like Applejack might consider tack as appropriate lingerie. It’s not like it’s functional for them, since nobody rides them in the traditional sense, but the suggestion of giving over control is sexy, and it’s just as elaborate as the best lingerie.
 
I haven’t researched to find out what plow horses would have for tack, but I might look into that.

@SillyFilly  
Thanks! I found an awesome diagram that I followed, for the most part. http://www.horsehealthusa.com/horsetackwestern.html
 
I got the idea because I’ve been working on drawing better anatomy, and from different angles, and I realized that some of the lingerie I sometimes draw on the ponies doesn’t actually make sense. So I figured I’d better go back to what horses actually can wear and get that figured out first.

Applejack in full working gear~  
Really nice work on the tack :D