This has been tested and it is working with Grub4DOS multiboot cd/dvd. I'm posting it here because I couldn't find it anywhere else, and I think is the right place. I like having different versions of Linux Mint Live in one DVD. Why carry 2 or more CD/DVDs when you can carry one?
Keep in mind that the ISO files were kept on the root of the folder making the ISO (in other words, the ISOs would be found in the root of the DVD once made). Also, I renamed the ISO files to keep it compatible with some older OSs when reading the DVD (I have other OSs booting in the same DVD, not just Linux Mint).
Here is the "menu.lst" settings:
title LINUX MINT 12 MATE X32
find --set-root /LXM12M32.ISO
map /LXM12M32.ISO (0xff)
kernel /casper/vmlinuz file=/cdrom/preseed/mint.seed boot=casper persistent iso-scan/filename=/LXM12M32.ISO
title LINUX MINT 15 MATE X32
find --set-root /LXM15M32.ISO
map --heads=0 --sectors-per-track=0 /LXM15M32.ISO (0xff)
kernel /casper/vmlinuz file=/cdrom/preseed/mint.seed boot=casper persistent iso-scan/filename=/LXM15M32.ISO
title LINUX MINT 15 CINNAMON X32
find --set-root /LXM15C32.ISO
map --heads=0 --sectors-per-track=0 /LXM15C32.ISO (0xff)
kernel /casper/vmlinuz file=/cdrom/preseed/mint.seed boot=casper persistent iso-scan/filename=/LXM15C32.ISO
NOTE: the settings for Linux Mint 12 did work with prior versions (v.10, 9, etc.) but it didn't work with version 13 or newer. Since the last version as of this posting is version 15, I didn't bother testing the settings for version 13 & 14. I suspect that it should be the same as version 15. These settings work with Linux Mint 15 Mate and Cinnamon x32/x64 - fully tested.
PLEASE: If anyone finds a better Grub4DOS menu settings, do let me know. These settings have been working flawlessly so far...