Since I am doing a wedlocke I put the pokemon who needs training or is going to do the best at the moment.
But I personally like mewtwo,lugia,mareep,crobat,feraligatr,ho-oh,charizard,tyranitar,dragonite,zapdos,moltres,articuno and Ninetales look awesome when walking behind you. Before my wedlocke I used to catch a lot of pokemon and put them in my party and walk around just to see how they look when they walk behind me.