Well, when Slivers return in Time Spiral, I finally hope for some support cards. Here is what I thougt about:
[Sliver Wrath]

Sorcery
Destroy each non-Sliver creature.
Sliver Cemetary

Enchantment
At the beginning of your upkeep, you may return target Sliver card from your graveyard to your hand.
Sliver Essence

Sorcery
You gain 4 life for each Sliver you control and 1 life for each Sliver card in your graveyard.
Sliver Burst

Instant
Put three 1/1 colourless Sliver Tokens into play.
Sliver Labotary

Artifact

, T, sacrifice a creature: Search your library for a Sliver card, reveal that card and put it into your hand. Shuffle your library afterwards.
Sliver Shrine

Enchantment-Shrine
Each Sliver has "At the beginning of your upkeep, put a 1/1 colourless Sliver token into play".
Just wanted to know what you thought about the general idea. Tribal-specific cards are quiete rare ("tribal-specific" meaning something like Goblin King, not Coat of Arms), and SLivers are rare too, so it's quite improbable.