add the GPG key using the following command

gpg --keyserver hkp://keyserver.ubuntu.com:11371 --recv-key 881574DE && gpg -a --export 881574DE | sudo apt-key add -

Or simply use the following command

sudo add-apt-repository ppa:bisigi

Update the source list using the following command

sudo aptitude update

Install all the themes using the following command

sudo aptitude install zgegblog-themes

or click on the following link

apt://zgegblog-themes

This will install the following themes

Showtime for Gnome

Balanzan

Infinity

Wild shine

Exotic

Tropical

Bamboo Zen

Ubuntu sunrise

Aqua Dreams

If you want to install above themes separately use the following commands

sudo aptitude install showtime-theme

sudo aptitude install balanzan-theme

sudo aptitude install infinity-theme

sudo aptitude install wild-shine-theme

sudo aptitude install exotic-theme

sudo aptitude install tropical-theme

sudo aptitude install bamboo-zen-theme

sudo aptitude install ubuntu-sunrise-theme

sudo aptitude install aquadreams-theme

Remove Themes

If you want to remove full package use the following command

sudo aptitude remove zgegblog-themes

If you want to remove each theme use the following syntax

sudo aptitude remove themename

Note :- themename is showtime-theme,balanzan-theme etc