This command will identify all OOXML files such as .xlsx or .docx in a directory recursively using the file command (looking for application/vnd.openxmlformats-officedocument MIME types) and move those to a different directory.

mkdir -p ../Documents && find . -type f -exec sh -c '
    case $( file -bi "$1" ) in (application/vnd.openxmlformats-officedocument*) exit 0; esac
    exit 1' sh {} \; -exec mv -v --backup=numbered {} ../Documents \;

Based on this StackExchange post. Also see How to move all images to other directory based on file content, ignoring the filename and How to move all videos to other directory based on file content, ignoring the filename and How to move all PDF files to other directory based on file content, ignoring the filename

This command will identify all audio files such as MP3s in a directory recursively using the file command (looking for audio/* MIME types) and move those to a different directory.

mkdir -p ../Audio && find . -type f -exec sh -c '
    case $( file -bi "$1" ) in (audio/*) exit 0; esac
    exit 1' sh {} \; -exec mv -v --backup=numbered {} ../Audio \;

Based on this StackExchange post. Also see How to move all images to other directory based on file content, ignoring the filename and How to move all videos to other directory based on file content, ignoring the filename

In backups you often see files like

0899d5d3c7f86344a8c085a053f5ca106482e6b8: Apple binary property list
089ce36beb618daa09263be95bd70880bd974dae: Apple binary property list
08b86c8bffdf6b12a0e4bd9f6807316afac51b53: Apple binary property list

without filename extension, that are not useful when you just care about the backupped files themselves and not any Apple-related metadata.

You can remove them using

file * | grep "Apple binary property list" | cut -f1 -d: | xargs rm -v

This command will identify all video files such as MP4s in a directory recursively using the file command (looking for video/* MIME types) and move those to a different directory.

mkdir -p ../Videos && find . -type f -exec sh -c '
    case $( file -bi "$1" ) in (video/*) exit 0; esac
    exit 1' sh {} \; -exec mv -v --backup=numbered {} ../Videos \;

Based on this StackExchange post. Also see How to move all images to other directory based on file content, ignoring the filename and How to move all audio files to other directory based on file content, ignoring the filename and How to move all PDF files to other directory based on file content, ignoring the filename

This command will identify all image files in a directory recursively using the file command (looking for image/* MIME types) and move those to a different directory.

mkdir -p ../Images && find . -type f -exec sh -c '
    case $( file -bi "$1" ) in (image/*) exit 0; esac
    exit 1' sh {} \; -exec mv -v --backup=numbered {} ../Images \;

Based on this StackExchange post. Also see How to move all audio files to other directory based on file content, ignoring the filename and How to move all videos to other directory based on file content, ignoring the filename and How to move all PDF files to other directory based on file content, ignoring the filename

This command line approach is rather primitive but will not overwrite files.

Run this repeatedly until all files are gone:

mv --backup=numbered **/* . && rmdir *

find . -name "*.thumb" -type f -exec rm -v {} \;

This is very useful in optimizing photo archives etc without changing the directory structure:

find . -name "*.jpg" -exec jpegoptim {} \;
find . -name "*.jpeg" -exec jpegoptim {} \;
find . -name "*.JPG" -exec jpegoptim {} \;
find . -name "*.JPEG" -exec jpegoptim {} \;