While the idea of a "Shroud Sliver" would be nice effectively giving Crystalline Slivers 5-8, I think a card advantage or card selection sliver would be even better. Something along the lines of "whenever you cast a sliver, draw a card" or "whenever a sliver comes into play under your control, you may look at the top 2-3 cards of your library and put them back in any order." An effect like either of these would really help at pushing this deck forward.