The first time I did this, I focused on some of the women in the Classics genre. I got good feedback from that, so I wanted to do another one - focusing on some YA characters. For the third one, I thought it'd be fun to focus on the four houses at Hogwarts. Gryffindor, Slytherin, Ravenclaw, and Hufflepuff. Again, these are just inspired outfits - mostly from their colors, and not necessarily from the actual characters in the books.
Scarlet and Gold
bravery, courage, and chivalry
Green and Silver
Blue and Bronze
Yellow and Black
patience, loyalty, hard work, friendships
Again, these are just inspired outfits. You can always mix it up, change it up, and do it differently according to your own personality and taste. I for one chose these outfits mainly because I personally would wear it.
Now I have to admit I had the most difficult time with Ravenclaw. For some reason, I couldn't get a "blue and bronze vision." Maybe because I don't feel like they really match. Ha.
Anyway, I encourage (and challenge!) you to do house-inspired outfits too. Either link up to your actual Polyvore account or do a separate post on your own blog. Either way, have fun!