Well you have gotten most of the wisdom on kilt pins. I went a long time without one, until I found one I really liked. Like McMurdo, I appreciate vintage pins and so all my kilt pins are vintage. One piece of advice that was offered a long time ago, and OCRichard touches on it, is that you can have too many representations of your clan crest, i.e. - hat badge, lapel pin, tie clasp, belt buckle, sporran flap AND kilt pin. One will probably suffice, and don't forget you are also wearing a clan tartan. So find a pin that you love.

Here is a photo of a couple of my pins. Forgive the quality, I took the photo as part of my inventory when I was moving homes, and so it is more for insurance purposes than to show off my bling. (My favourite is on my kilt, so not in the photo).