This is something I had a problem with when I first started doing it too but not because I wanted stuff to represent the show/movie, but because I wanted all the decks to have similar powers and abilities. That's stupid now, obviously, if every deck has Movement, DD, Power D, Power A, Drawing, Discarding ect then every deck plays the same and aren't fun.

However, the problem becomes when a set becomes too large - like the current star wars set for example. There's bound to be decks where things overlap. Greedo the younger and Dash Render spring to mind right now - mostly because I just looked at them yesterday. When I started the 'Last Airbender' Volume II I struggled for a long time to get deck themes down but it something that comes from practice and research on things like this. And I still worry that some of them are too similar and/or not good enough.

One easy way I've found to balance a small set is to limit certain things to certain characters. Like only one character gets DD, or only one character gets discarding ect. Which is easy on a small scale but becomes more difficult as it gets bigger.

The above decks aren't actually terrible when you look at them, they're just muddled and don't have a theme. Still, not all decks have a theme, some just play a well rounded game.