Whats the difference between official and unofficial images?
Official images are built by a member of the Debian CD team and have undergone some testing to ensure they work. Once they have been released, the images never change – if they turn out to be broken, a new set with a different version number is released. Unofficial images can be built by anyone – CD team members, other Debian developers or even advanced Debian users. Typically, they are more up-to-date, but have received less testing. Some have new features (e.g. installation support for new hardware), or contain additional software packages which are not part of the Debian archive.