The directors and the production team for LoliRock decided to have those symbols to represent each of the respective realms. The specific reason for why they choose these symbols, we do not know. I've searched through Team LoliRock's tumblr if they have any information regarding it, but no dice. :(
Ephedia is classified as a realm since it is one of the many realms/kingdoms and the capital of the planet, Ephedia. I know it is confusing but all you need to know is that Ephedia is two different locations: 1) a planet, and 2) a realm/kingdom. Even though the realm and the planet shares the same name, they are both different locations based on which of the two are being referred to. It is similar to a tv show, W.I.T.C.H, having the planet of Meridian with a capital under the same name.