Yes to do what you need you simply need to change the xdg configuration for each existing user like so:
~/.config/user-dirs.dirs
XDG_DESKTOP_DIR="$HOME/Desktop"
...
XDG_MUSIC_DIR="/home/common/Music"
XDG_VIDEOS_DIR="$HOME/Movies"
And to make this something available to all users created simply edit this:
/etc/xdg/user-dirs.defaults
DESKTOP=Desktop
...
MUSIC=../common/Music
VIDEOS=Videos
To modify the permissions, this bit is tricky because you need to make sure that all files created in these directories remain editable by everyone. I found this interesting guide on the subject:
http://www.centos.org/docs/2/rhl-rg-en-7.2/s1-users-groups-private-groups.html
Which suggests doing the following to make the permissions sticky as well as adding the users all to a common group:
chown nobody:users /home/common
chmod 2775 /home/common
usermod -a -G users user1
You may want to change the umask setting to allow all files created to be modifiable by the anyone in the users group in that directory, edit /etc/profile and go to the bottom and change umask 022 to umask 002 This is considered secure since all users have their own primary user and really only effects shared directories like this one you want to make.
Let us know if it works well enough.
The home directory must be recreated, and with the right permissions. This requires that you boot your computer into recovery mode (aka safe mode) when the starts press and hold the left Shift key and select Ubuntu, blah (recovery mode) from the list.
Once you're into the recovery mode in the system you'll see a menu, select "Root - Drop into a root shell prompt". you'll need to use some commands typed in to recover the system so write them down:
mkdir /home/username
chown username:username /home/username
Replace username with the username you need. To confirm that this is the directory you need and that it will work do:
cd ~username
And that's it, type reboot to get out and reboot the computer. Once you're back in your computer's user's desktop, you can go looking for your files; hopefully they've not been deleted as your description makes it sound like they've just been moved somewhere else. Find them and move them back using Nautilus, or if you don't have permission to move the files then use gksu nautilus to give yourself god like powers (be careful!)
Best Answer
If you drop any files in this folder, for example
then when you right-click and create a new document, you can select any of these files as a basis for the new file - i.e. a template.
For as long as I remember, this has always been a standard feature on many desktops such as Gnome.
If you have deleted the folder and need to restore this functionality:
Check that there is a line containing the following - if not, add this line.