Hmmm I do not know much about commands but correct me if I' wrong:
mkdir /tmp/debian-temp - this makes the folder in tmp just for purpouse of copying
mount /home/user/MyDocs/your-easy-debian-image-file.ext3 - this mounts the image
/tmp/debian-temp - this moves me form / to debian-temp
mount /dev/mmcblk1p1 /.debian - this mounts the sd card
cp -a /tmp/debian-temp/* /.debian/ - this is copying files from temp to sd but what files as no command has copied any files to debian-temp?