Since this thread i still up, i'll tell you, I use Glitchy's MES ( i would suggest doing it with XVI32 at first so you get to see how it works in game.
But yeah, the Sheath ID's are as followed:
1 = Two Handed Sword (on the back; tip down) ( also used for warglaives Set both to 1)
2 = Staff (on the back; tip up)
3 = One Handed Sword (on the side)
4 = Shield (on the back)
5 = Enchanter's Rod (??? never tried that)
7 = Off Hand
But yeah, those are the Sheath id i could find from ProjectMangos.org ( even if mangos is designed to be a private server, they still use the same sheath IDs, dont worry. )
Hope this helps!