Speaking of credits music (these suggestions are all chill out, relaxing songs):
Joshua Morse - Samurai Discotheque (OC Remix) - I am absolutely in love with the bass in this song. It is so funky. It's a remix of the "Can't go home again, baby" song from Ragnarök Online.
Audix & Tweek - Day's End (OC Remix) - This is a remix of the end credits theme from Mario Kart 64. Honestly, this song is amazing. I love it so much. Even if you don't normally like relaxing music, or if you just plain don't care about what the credits music should be, you should check out this song.
Blue Magic - New Beginnings (OC Remix) - It's a remix of the Deep Jungle theme from Kingdom Hearts. This is another one of those songs that I think everyone should listen to, even if they like played Kingdom Hearts and hated it. That said, for some reason most people I talk to who have heard of OC Remix have already heard this song, which makes it sound almost cliché to me for credits music :x
Only 3 suggestions this time, because all of my other possible suggestions are from games that have character representation in brawl (and let's face it, hearing the Stickerbrush Symphony song or something in a Bowser video would just be plain weird, even if it is just the credits)