With my Modern snow-related deck, I really like Rime Transfusion. It's a solid boost that can effectively make your guys unblockable. Also, +1 for the skeleton deck! I'd been thinking of making one myself, but you beat me to the punch! Also, Undying Evil might be nice. It'd offer protection against "Cannot be regenerated" and it'd essentially be a mono-black regen cost (cheaper than most of your guys'), and it'd give counters, too.