It really depends on the scene, Like oNITESkye said, keep it minimal. Smash 3 textures might be okay, but I'd hold off on that until your scene gets off the ground, then you can just keep them on one setup.
Music packs should generate hype without being too distracting, in my opinion. For example, my pack sticks to remixes of game tracks, high energy stuff but no lyrical tracks or music straight out of other games (I made a few exceptions on casual stages).
Treat the first two rows of page 1 as tournament legal, even if you end up running a smaller stagelist. We run a 10-stage list that works perfectly; the full 14 is a bit much. Hell, any stage that could possibly be tourney legal in a future stagelist in your scene should be treated as such (Smashing Grounds ran Metal Cavern for a while, for example).
I'm going to blatantly advertise the build I put together for our local scene on campus. I avoided character textures, aside from the fixes posted in that other big thread in here.
Character Select: Do whatever you want with this, just keep it clean. If your build will be used by a lot of people in competitive play, make it look professional. I highly recommend putting in a background icon to represent your scene:
http://imgur.com/a/qLsCl
Stage Select: Colored borders are pretty nice, as well as stage striking rules and such.
https://imgur.com/a/Wg2qZ
Stage textures: Here's where things get interesting. Like I said, keep them minimal, representative of your scene without being too distracting. Smashing Grounds did a great job of that, and I took a lot of inspiration from them:
https://imgur.com/a/SePQV (The Fountain of Dreams screenshot is outdated; that sky texture was causing freezes, and it looks obnoxious anyway. I kept our logo slapped around the pillars instead of stars though).
Music: Here's my music pack. I would also recommend putting a list like this together to throw in with your pack. I personally changed a lot of tracks on both legal and casual stages, but you can stick to tourney legal stages to keep the size down (my pack is JUST under 2 GB). Like I said before, high energy stuff without being too distracting. Personally, I like to keep the tracks relevant to the stages, showcasing some awesome remixes.
https://docs.google.com/spreadsheet...jy4hbu-Y4gD4LEPev0yK4o7Ok/edit#gid=1322807755
RESOURCES:
CSS and SSS modifications:
http://smashboards.com/threads/proj...ensive-tutorial-and-sample-stagelists.382890/
Brawl Managers, including SSS editor for moving the icons around to better fit your scene's stagelist:
http://www.lakora.us/brawl/BrawlManagers-3.5.zip
BRSTM converter, for making your own tracks:
http://www.lakora.us/brawl/brstm/
Photoshop is highly recommended. I used to try to work with this stuff in GIMP and it was painful.
Be careful on Brawl Vault. A lot of stages haven't been updated to 3.5, and a lot of character textures actually change the models slightly.