You will be able to earn other surnames through achievements. These can be based on heroic deeds, skill proficiency, or even humorous events. Some of these will even be unique to your bloodline. However, they will not be customisable. There will be a lot of choice with surnames and the various dynasties in the world but if you want a specific surname you will need to go for the Bloodline tier or above or convince a friend with it to get your surname into Elyria.