Just like Graham mentioned above, Shatter has many different object models already built in (including Puzzle Pieces) that may be suitable.
Like YikesMikes mentioned the other day, https://forums.creativecow.net/cgi-bin/new_read_post.cgi?forumid=2&postid=855004
[yikesmikes] “If you want total control, I suppose you could slice the photo up in Photoshop putting each puzzle piece on a layer, then import into AE, then manually keyframe the pieces (each their own layer now in AE) when you want them to fly off.”
So you can create a custom map in Photoshop and then use that as your target layer for Shatter in AE. For something simple and quick, you can take your image into Photoshop and use the path tool to create custom shapes over your image. After each shape is closed, make a selection from that path, then cut them out onto their own layers (PC: Ctrl+shift+j) or just Ctrl+j if you want to leave your original untouched. Save that out as a .psd file and import into AE as a Photoshop comp and animate to your hearts content.
Otherwise, for greater control I believe if you fill (white over black) each path or image “piece” with varying whites to black (grey inbetween) and then save that out as a flat image to import into AE, Shatter will animate your puzzle pieces (depending upon your settings) each color individually from whites to grey to black respectively.
Sorry it’s been a while since I’ve used Shatter otherwise I probably could give you more detail. So I hope I haven’t directed you incorrectly :>)
Alien Skin makes a package for Photoshop called Xenofex, and it has a plugin that creates the common puzzle style pieces. You can use that to create a quick and easy map as well.
Hope that helps ya,
Tom