Best way make a jigsaw shape out of a larger image

1. Create your jigsaw piece edges as Bezier curves, either manually, programmatically or by pulling them out of an Inkscape SVG file. Make as many as you need, at least 20 but more is better.

2. Join 4 of them up to make edges of a tile mask, one per tile on a single texture, with spacing around each tile. I used Windows Geometry.

3. Apply the selected mask to the picture at the correct offset and you get a tile.

Sorry, but that turns out to be the easy part. Getting good visuals when dragging tiles around is really hard.