The SA box on the sleek is a few shades lighter than the backgrounds I designed. You'll see that in the Revelation expansion set I'm working on, which uses the sleek template.
Also I decided to use a visual rarity indication similar to MTG. The set symbol is colored based on the rarity.
White - Common
Blue - Uncommon
Silver - Rare
Gold - Ultra Rare
Again, you can see that in the upcoming revelation set.