We prefer #4 to #5 because of the matte background. They are both a bit plain, we really like the idea of mallets but maybe they don't need to be constrained in a box. Making them into a 3-D image might bring some more life to the design, along with some more colors like orange and yellow.
#6 looks great, its exactly what we were talking about in the earlier comment. Bringing some more colors and maybe a bit more shape to the mallets would make the design stand out a bit more.