I suggest you convert your WAV files to mp3 for uploading. I notice that if you use the free version of Box.net, there is a limit of 25MB per file. A WAV file is typically 10MB/min in size, so you can easily exceed your upload limit in a single file. A 128 bitrate mp3 is about 1MB/min so a significant saving, though there is a slight deterioration in quality. Obviously you should keep your original WAV files and not delete them.

ImageShack seems to be restricted to video/image files only. See their terms of service here

Another possibility is to upload to You Tube. (I have seen the occasional audio only file). You can restrict the files to your band members by setting them as "Unlisted" and send them a link or as "Private", in which case they have to be a You Tube subscriber and you have a limit of 25 people who can view your private files but Private files are more secure. I use "unlisted" for videos of my granddaughter so I can let my daughter and son-in-law see them.