Just made these three wallpapers from the flags for the three city-states (and as far as I'm concerned, are for free use). They are for my Widescreen Monitor but can easily be shortened for the other kind. Let me know what you think and if you use one (or more!)
Gridania:
Spoiler: show
Limsa Lominsa:
Spoiler: show
Ul'dah:
Spoiler: show
UPDATE: From the newer Fansite Pack.
Imperial Wallpaper:
Spoiler: show