When and if Yoshi decides to do it for some reason.
Personally, I don't see what's so awesome about them.
Sure, they're pretty good, but they seem to be getting a bit more praise then they should be in my opinion.
Yoshi Head- Well, it looks like a perfect remake, but I don't really have any use for a Yoshi Head...
Fez- Don't really have much use for that either, and the face has a really weird color; personally, I prefer consistancy.
Dunce- Again, odd coloring, but the cap could use some shading. Looks flat.
Dopey- The tooth looks really... odd. Not sure what it is I don't like about it though. Beside, again, coloring of course.
Domo-Kun- Good, but I don't have much use for it, and a different pose could be good...
Bowser Head- Look at Yoshi Head and Domo-Kun...
Wink- It's shaded down-up, giving it a concave-disc look, the shape of the smile should be slightly more rounded(shading usualy helps for that), the right eye looks creepy, and the left eye could atleast be slanted.

looks perfect to me. His mouth is shifted a bit to the right, and you can see his raised eyebrow above his eye that isn't abnormally huge.
Undecided- As with the rest, it looks like a flattened coin that's been bent. As with the rest, again, the eyes are huge. Still, it's better then Dopey or Wink.
Tongue- I like how the

smiley still has a smile, and how it has happy looking eyes instead of giant, and(literally) retarded looking eyes...
LipSealed- ... The middle of the mouth just looks... weird...
Laugh- His mouth just looks creepy... maybe it's the fact that it's completely black...
Embarresed/Sad/Undecided- Actualy, I think Undecided makes a better frowny Emote then Sad. And Embarresed just looks like a Sad with more detail/expression.