The Spark of Light is just once per account. You can use it on one character, but beyond that character, any other characters you decide to make or remake (even if you delete and make that character you already used it on again) you'll have to level normally without the benefit of the Spark of Light. It's a one-time gift only and one-use item. As far as emblems and the like, if you received them after Update 2.0 came out, the emblems and shaders should be available from the relevant kiosk in the Tower. Concerning other things such as items and the like for Preorders or Collector's edition, the items themselves are only awarded once, but there are some posts from people saying they didn't get all of the character items for each of the three classes for some of the specials. But if you received an item that isn't specific to any specific type of character, then you most likely will only receive one of that item, and if you then subsequently deleted it, it's gone for good unless it's an exotic, then there should be a blueprint of it available at the relevant kiosk.