Vintage silver and enamel souvenir travel shield charms are highly collectible today. Most travel shield charms have enameled pictures of landmarks, animals, flowers, or birds, along with the name of the travel destination on the front. Travel shields are typically made from European silver with a grade of 800 to 835, or 925 sterling silver. There are also very distinctive British charms that have a baked enamel finish on the front.
I've been amazed at the variety of different travel shield charm collections I've seen. There are the expected "Places I've Visited" varieties. And I own a couple of different types of British Zodiac sets with the baked enamel finish. Although they aren't travel related, I consider the Zodiacs an example of shield charms. Additionally I know of collectors that arrange shields of a particular color on their bracelets, or categories of images such as all flowers, or all animal heads. There are also collections from different parts of a specific country, or a collection of cities in an area, various national parks, different zoos, and bust / head images of famous people. And a friend of mine collects just British baked enamel shields.
The best thing about shield charms is there is an abundance of them, both old and new, available in souvenir shops around the world, in antique shops, and on the internet. As a result they are quite inexpensive and it's a great way to get introduced to the world of charm collecting without spending a lot of money. I recommend starting with a few examples that appeal to you. At that point you can decide how you want to proceed with your collection. Your tastes may change several times in the process of experimenting with different arrangements. Above all remember to have fun with your charm collection.