The wav2png droplet is now a sandboxed application so it can be deployed via the Mac App Store. You can either get it there or download it here. Because the droplet is sandboxed, the png image files will be stored to ~/Pictures/wav2png (instead of to the same folder as the .wav file is stored).
If you got five bugs to spare, you can download the droplet via the Mac App Store
Otherwise you can download it here (for free of course):
wav2pngDroplet.zip