As stated above I would go with a pair of clowns, I've always put a pair of clowns in all of my tanks. Just be careful on types of clowns some are more aggresive then others. I would go with 2-3 wrasses to add movement and color. You could get a tang even though a lot of people will disagree, but a small tang and after 2-3 years you could upgrade or find a good home for it because it will out grow a 63g tank. Green chromis for a little school of fish, Gobies, blenny haha there are a lot of choices you could go with. might be good for you to put a list of fish you like and have people help you pick fish that would be ok together.