Yes, you can copy your own multitrack session files to use with the ICE-16/ICE-16D. You must use the folder structure (Record > Song_x) when adding your own Wav files.
The important point to understand is that ICE-16 will playback your tracks sequentially in the order they were *COPIED* to the USB stick/drive,
*NOT* in the alphabetic/numeric order in which they are named.