You're probably correct that "Filesystem" cannot be changed without hacking the source code.
But I have 4 linux systems installed, and in pcmanfm they show up as "52.4GB volume", "209.7MB volume" etc, and it's a challenge to remember what's what. I use gparted to label them as "ArchBoot," "Fedora12Home," and so on. I don't use nautilus but I suspect it will use labels also if it finds them.
LVM might pose a problem for gparted. I don't use LVM. Palimpsest might work, haven't tried it. At the lowest level, the e2label command will do the job, it's part of the e2fsprogs package. Look at "info e2label" for instructions.