This helps me find unused images in a Rails project. The echo statement never executes, so there's a glitch, but the output was helpful nonetheless. I'll try to improve later.

find-unused.sh

#!/bin/sh

PROJECT="" # Fill this in
IMAGES="$PROJECT/app/assets/images"
VIEWS="$PROJECT/app/views"
CSS="$PROJECT/app/assets/stylesheets"

for image in `find $IMAGES -type f`
do
    name=`basename $image`
    echo "Searching for $name [originally $image]"
    if ! ag $name $VIEWS $CSS; then
        echo "$image is not referenced"
    fi
done