Bucklers
Best you can do, is to check out the wardrobe in your Bank in game.
Failing what Mike said, I find this site: http://argos-soft.net/GW2/WeaponGallery/index.php?weapon=16&lang=en very useful. Obviously it doesn’t give the scale of the weapons compared to the character, but I find it to be the best option if I want to look through all skins at a glance.
As for suggestions of skins to use, the smallest/roundest shield skin I can think of is the Aetherized Shield. Unfortunately, it’s one of the most expensive shields up there.
Call of the Commissar or Guardian of the Six are probably your best options. Neither are quite buckler size but they are the smallest round shields I have seen. That or the standard ugly little wooden starter shield. If you aren’t concerned with it being round, the golden wing/seraph shields are very small and sleek, kind of form fits to your arm. Best of luck!
(edited by Relair.1843)