A standardized size would be good, but people would still be free to be creative and use whatever kind of emblem they wanted be it shield, flag, crest, etc.
As with Fury's example, you would have a standard block size but your shield may simply not fill it all up in which you have transparency for that space. This way everyone retains the customization and creativity we all enjoy in realm banner's, but we also gain a more aesthetically pleasing map presentation.
And yes, these maps, and especially even the history videos could be great to help market the game. Exactly as Tom presented it: Check this out, a 8 year's worth (and counting) of persistent game world history.
