Courtesy of some very helpful ImageMagick hints by Anthony Thyssen, a bit of magic to create a “stack of polaroids” effect. Here it is applied to one of my all-time favourite photos.
convert -size 400x180 hatching.jpg -thumbnail ‘200x90>’
-bordercolor white -border 6
-bordercolor grey60 -border 1
-bordercolor none -background none
( -clone 0 -rotate perl -e 'print rand() * 30 - 15' )
( -clone 0 -rotate perl -e 'print rand() * 30 - 15' )
( -clone 0 -rotate perl -e 'print rand() * 30 - 15' )
( -clone 0 -rotate perl -e 'print rand() * 30 - 15' )
-delete 0 -border 100x80 -gravity center
-crop 200x160+0+0 +repage -flatten -trim +repage
-background black ( +clone -shadow 60x4+4+4 ) +swap
-background none -flatten
-depth 8 -colors 256 -quality 95 polaroid_stack.png
