In Natural Language Processing and related disciplines, it's common to see an "overlaid pages" image included as a node in a flowchart of a system:
_____
| ___|__
| | ___|___
| | | |
| | | |
|_| | |
|__| |
| |
|_______|
The image is meant to represent a corpus or some other large collection of text data. How can I draw something like this for a Tikz flowchart?