What I would do is go to artnails.com and by thier nail art stuff. They show you different shapes you can make with thier brushes. once you get the shapes down with paint, you can see how you would have to design the wings and body of a butterfly. Simply make the same shape with your acrylic one wing at a time and build your butterfly one section at a time. I wound start by making the wings almost touching, and then make the body in the center but ontop of the wings. I think that would make it look even more 3d. If your not good with blending colors, just paint the butterfly and cap it with gel, or top coat, or clear acrylic.
Tess