1a. Installing Mate
If you are running 14.04 fellow this instructions.
Click this link to install the Mate
package, find it in the Ubuntu Software Center, or type sudo apt-get install mint-desktop
in a terminal. There are more instructions here
If you are running 12.04-13.10 fellow this instructions.
Type this in a terminal
# this add the repository
sudo add-apt-repository "deb http://packages.mate-desktop.org/repo/ubuntu $(lsb_release -cs) main"
sudo apt-get update
sudo apt-get install mate-archive-keyring
sudo apt-get update
# this installs base packages
sudo apt-get install mate-core
# this installs more packages
sudo apt-get install mate-desktop-environment
If you are running 14.04 fellow this instructions.
Click this link to install the Gnome Flashback
package, find it in the Ubuntu Software Center, or type sudo apt-get install gnome-session-flashback
in a terminal. There are more instructions here
If you are running 12.04-13.10 fellow this instructions.
Click this link to install the Gnome Fallback/Panel
package, find it in the Ubuntu Software Center, or type sudo apt-get install gnome-panel
or sudo apt-get install gnome-session-fallback
in a terminal. There are more instructions here
Click this link to install the XFCE
package, find it in the Ubuntu Software Center, or type sudo apt-get install xubuntu-desktop
in a terminal. There are more instructions here
Ubuntu has an XFCE spin called Xubuntu it is recommended to install it from the official image (.iso) that can be downloaded at this page.
Step 2. Make them look like Ubuntu 10.04.
2a. Making Mate
You need to get the Ambiance Theme so open up a terminal and type this in.
cd ~/Downloads
wget http://dl.dropbox.com/u/72782740/debian/ubuntu/ambiance-mate_12.04_all.deb
sudo dpkg -i ambiance-mate_12.04_all.deb
Or download this file, click here to download and install it though Gdebi, Ubuntu Software center, or...
After it is done install, change the Theme to Ambiance MATE so open the Appearance preferences (located under System -> Preferences) and select the Ambiance MATE theme.

This is how It is going to look like

After that you now need to chance the wallpaper to the 10.04 one. so first you need to get them. So open up a terminal
cd ~/Downloads
wget https://launchpad.net/ubuntu/+archive/primary/+files/ubuntu-wallpapers_0.31.3_all.deb
sudo dpkg -i ubuntu-wallpapers_0.31.3_all.deb
Or download this file, click here to download and install it though Gdebi, Ubuntu Software center, or...
After it is done install, change the wallpaper to the default in 10.04 so open the Appearance preferences (located under System -> Background) and select the the default in 10.04 wallpaper.
*Sorry I couldn't find a image for this micro-step.
You need to get the Ambiance theme if you don't ready have it. It isn't any different from the stock one that you need. If you don't have it click here to download it And just install it though Gdebi, Ubuntu Software Center, or tools like it. Finally you just need to chance the wallpaper to the one in 10.04 and you do that by just opening a terminal and type in
cd ~/Downloads
wget https://launchpad.net/ubuntu/+archive/primary/+files/ubuntu-wallpapers_0.31.3_all.deb
sudo dpkg -i ubuntu-wallpapers_0.31.3_all.deb
Or download this file, click here to download and install it though Gdebi, Ubuntu Software center, or... And it is no difference into changing it from normal unity. More Info
2b. Making XFCE
Making the panels look like Gnome 2
First, Remove the the button panel by right clicking on it and select Delete. Add the Show Desktop, Window Buttons, Workspace Switcher and Trash Applet to the new button panel. Now we are done with the button panel now it is time for the button one so chance the panel size to 24px by right clicking on it and select Panel>Panel Preferences. Rename “File Manager” menu into “Places” by opening the handy terminal and type in sudo nano /usr/share/applications/xfce-settings-manager.desktop
find the entry Name and change the entry into this Name=Settings Manager
→ Name=System
save it and close it. Now Right click on the Panel Select Panel Preferences Than Items. Remove all default items and left 8 eight items : Applications Menu, Separator, Notification Area, add a separator between Applications Menu and Notification Area to be Expand by click the item, and click edit item by select Edit the currently selected item button at the bottom of Panel Preferences menu. Then, add two Launcher items and move them to the position after Applications Menu item. Set them to Show Label Instead of Icon, by clicking Edit the currently selected item>Advanced> Show Label Instead of Icon. Now, edit each launcher and add the two main applications. For first launcher, add the Places items by clicking Edit the currently selected item>General>Add new item, search and scroll down to get the Places item. For the second launcher, do the same but put the System item (that we have edited before from the xfce-settings-manager desktop menu).
Now, we have a good looking Gnome 2 panels.
Now We are going to change the theme to Ambiance
You need to get the Ambiance Theme so open up a terminal and type this in.
Add Ravefinity Project PPA
sudo add-apt-repository ppa:ravefinity-project/ppa -y
Update package information and install ambiance and radiance themes
sudo apt-get update && sudo apt-get install ambiance-xfce-lxde radiance-xfce-lxde
Install other colors variations (blue, green, purple, ...):
sudo apt-get install ambiance-colors-xfce-lxde radiance-colors-xfce-lxde
Or download this file, click here to download and install it though Gdebi, Ubuntu Software center, or...
After it is done install, change the Theme to Ambiance.

This is how It is going to look like

After that you now need to chance the wallpaper to the 10.04 one. so first you need to get them. So open up a terminal
cd ~/Downloads
wget https://launchpad.net/ubuntu/+archive/primary/+files/ubuntu-wallpapers_0.31.3_all.deb
sudo dpkg -i ubuntu-wallpapers_0.31.3_all.deb
Or download this file, click here to download and install it though Gdebi, Ubuntu Software center, or...
After it is done install, change the wallpaper to the default in 10.04 so open the Desktop Settings (Right on the desktop -> Desktop Setting) and select the the default in 10.04 wallpaper.
You need to get the Ambiance Theme so open up a terminal and type this in.
sudo add-apt-repository ppa:noobslab/mint
sudo apt-get update
sudo apt-get install mdm mdm-themes
During the installation you will get a window asking you to choose your default DM, like the one in the print screen. Choose MDM.

And That is it!!!
Sources