For silk banner making, I learned everything I know from Ms Hunydd, for heraldic display, I have just picked up bits and pieces along the way, researched fragments and made some banners. There are some out there who are way better versed on the subject that I.
However, seeing as I've been asked, I'll attempt an answer.
Wishwords, over at the heraldicdisplay LJ community, asked "Could you do a post explaining how you decided on the various banner designs? What period guidelines influenced you? How do you decide which device goes where on mixed heraldry?"
And all the past Baron and Baronesses of Rowany
So, as you might imagine, creating a look that is unifying yet unique provided some difficulties. To solve the problem, we decided to have the Lochac populace badge (Lochac device without laurel and crown) on the hoist. Then we decided that green and white are the predominant colours for Rowany and we should use them as well down the fly.
Now usually, it is period practice to have the main charge of the device over the background of the fly colours. However, in this instance, where we had issues with mixed heraldry, we often found that we had an argent charge that we wouldn't be able to separate from the field, making for less effective heraldry and display. To overcome that problem, we opted to put the main charge of the individuals' devices over one of the main colours from their device (except for Hrothgar, where we used vairy en point...which was hugely effective). From what I can tell, this is not period practice, however, for the purposes of this project, it seemed to be the best solution, given the time constraint that we had.
To keep with a Rowany theme, we found some pilgrim badges, which we adapted and used along the fly.I cannot remember which website this picture came from. If you know, please tell me so I can attribute the right people.
So this is basically what we did. I will post again soon with some research, however, if you look at the links in my sidebar, you will find more answers there.