Now that I've been feeling all Middle Earthy, I've been scouring Pinterest for suitable inspiration for shield and flag designs.
When you Google Elvish heraldry you run across these designs by JRRT himself:
A lozenge is for males and circles are for female characters. But they look like quilt designs to me and aren't quite bold enough for flags.
Rohan and Gondor naturally have the most results with their clearly defined symbols. This page being a fine example.
But as you can see there are some nice elvish designs in the mix too. Plus one that might do for Angmar.
Of course trees and stars aren't just for Gondor. The design over the west gate of Moria as reproduced in most editions of The Lord of the Rings mixes motifs from both the realm of Kazad-Dum and the elvish realm in Hollin.
This gets me thinking about the two trees of Valinor, pictured in this lovely design I found:
The two trees could be a nice design for a flag. Then on the shields we could have one tree something like one of these:
Perhaps in a gold on white? Gold and/or silver on blue?
Noe to practice on paper before trying to paint it on a shield less than a half by three quarter of an inch!