Hey Nathan,

I'm sure you could take some nice pictures of your own tartan kilts (Various clan tartans)
The clan crests (I seem to remember are copyrighted by gaelic themes, maybe ask them/The Wizard might know better)
The Chiefs arms, ask the chief?
For the rest, maybe some Xmarkers have what you need.
If I had what you need I would happily give them to you, unfortunately I don't.

The problem with the pictures that are "creative commons" is, that they are not to be used commercially. At least that is how I understand "creative commons".

Anyway, I wish you good luck and I would enjoy to see the finished book