community.linuxmint.com

Check /etc/issue, /etc/issue.net, /etc/lsb-release and /etc/linuxmint/info.

etc/issue
Linux Mint <version> <codename> \n \l

/etc/issue.net
Linux Mint <version> <codename>

/etc/lsb-release
DISTRIB_ID=LinuxMint
DISTRIB_RELEASE=<version>
DISTRIB_CODENAME=<codename> <-- no capital letters, very important..
DISTRIB_DESCRIPTION="Linux Mint <version> <codename>"

/etc/linuxmint/info
RELEASE=<version>
CODENAME=<codename> <-- no capital letters, very important..
EDITION="<desktop> <num_bits>-bit"
DESCRIPTION="Linux Mint <version> <codename>"
DESKTOP=<desktop>
TOOLKIT=<GTK or QT>
NEW_FEATURES_URL=http://www.linuxmint.com/rel_<codename>_whatsnew.php
RELEASE_NOTES_URL=http://www.linuxmint.com/rel_<codename>.php
USER_GUIDE_URL=http://www.linuxmint.com/documentation.php
GRUB_TITLE=Linux Mint <version> <desktop> <num_bits>-bit

The release notes and new features URL for non-gnome editions follow a slightly different pattern, for instance Linux Mint 10 KDE links are:

NEW_FEATURES_URL=http://www.linuxmint.com/rel_julia_kde_whatsnew.php
RELEASE_NOTES_URL=http://www.linuxmint.com/rel_julia_kde.php

Links aren't valid until a few days before the release, so don't worry if you get a 404 error while testing... you're just ahead of the game :)

For the Grub title, if the desktop is Gnome, it doesn't mention it.