Black-Lyne,
Number 4 lost points as others pointed out they may have seen something too similar in other designs. Here are some other comments from the group.
15 has promise in my eye, if we can encourage them to develop some form of a letter mark on the basis of that type of look as well.
but it sort of lacks punch or brightness of color? If you look at 10 and 13, their color is what attracts me.
I almost envision something like a yin yang design with leaves to represent each side and the whole to represent the earth. Is that getting too specific?? Too abstract?