Hard to say without more info. Did you simply install and then immediately activate it, and noticed this mobile image problem right away? Or did you set up mobile groups under w3tc and then the problem began? Are you in minify Auto or Manual mode (or is minify even enabled)? Are you using a CDN to serve your images?
When the images disappear, have you checked your source to see what links the images are trying to retrieve? Are these links broken or malformed?
Have you tried enabling w3tc but disabling Minify to see if things now work? What about disabling page cache but leaving on Minify? Just trying to start the process to help narrow the problem down.
