These are Faenza-style Pardus, MeeGo, Linpus and Android-x86 icons for burg theme "Fortune". It is so simple to use them for "burg". In order to install "burg" which is "the grub-alternative graphical bootloader" open a terminal window and add "burg-ppa" by typing:

sudo add-apt-repository ppa:bean123ch/burg (just press "enter" and type your administrator password when prompted! , then;
sudo apt-get update && sudo apt-get install burg (during the installation a window can be opened to ask you where to install burg such as /dev/sda or /dev/sdb; then choose the disk where your ubuntu os is installed! (most probably /dev/sda) )

After this step, download and install "Fortune" theme:

http://gnome-look.org/content/show.php/Fortune+-+BURG+Theme?content=128929

After installing Fortune theme, open a terminal window and browse to the folder where you've downloaded tar.gz archives (such as "Downloads" or "Desktop") and type:

cd ~/Downloads
sudo cp Icons4Fortune-by_sedaTurca.tar.gz /boot/burg/themes/fortune/icons
sudo cd /boot/burg/themes/fortune/icons
sudo tar vzfx Icons4Fortune-by_sedaTurca.tar.gz
sudo rm Icons4fortune-by_sedaTurca.tar.gz
exit

and finally launch "sudo burg-emu" from terminal and select "fortune" theme, enjoy your new icons