Blood Pet
A way to double up on creatures for only B? It isn't acceleration but it's essentially a 'free' creature that provides B to play Shadow/Imp and even pays 1B for Gurmag by itself, in order to trigger Vengevines. Testing shall commence! I think it's a better way to go than Hollow One, possibly not as good as Birds of Paradise. I do like that it can be played t1 and still allow a t2 Buried Alive with a 2nd land drop.
EDIT: Just another round of disappointing attempts at this kind of deck. *sigh* It's fun to attempt but it's depressing to fail.