out of the choices i would say top pic, however i'd like to see other angles. personally i think if you stood the one from the last 2 pics up it may look better, more like roots.
kinda off topic but the mr. burns comment reminded me of a piece i was going to use until i messed up the curing and it rotted. completely looked like a hand half closed being decayed. i know its weird but i thought it would be cool to place it behind some plants so it would look like a body under the substrate that was partly exposed. creepy theme tank i may still try