I'll have a look but I'm not a big fan of seperate shields so we might try a quartered shield as well.
In that case, I'll got nuts with quarters. Have, say, your current shield (lets call it your Family shield) in 2 quarters, one for Lorraine and one for Metz?

Can I have a white subshield with this boar on it: http://commons.wikimedia.org/wiki/Fi...ure_-_Boar.svg

in front of the Lorraine shield (assuming they'll have me) please.
Can do. Be aware that so far nobody other than Dukes have used their House shield though. So feel free to design your own if you want.

nevermind, it should be fine if you just move the Fleur de whats down a bit more
Good. I think its busy enough as it is