Destron is a Hydralisk (obviously) with Cybernetic bits integrated all into his body.
Notable places to have these would be his shoulders, arms, head, back, and chest (read below
His chest is pretty much in two halves due to them opening up to launch or store the minions (think of Bomb Bay Doors).
One eye is cybernetic and something like the eye of this http://browse.deviantart.com/art/Shockwave-268808316 (but you know smaller).
On his right shoulder he has a launcher that looks like this
This but much more Zergy (obviously) and with cybernetic bits as well as a slightly more catlike head and two eyes. His tail is very long and ends in a blade like tip.
This but much more Zergy (obviously) and with cybernetic bits as well as batish wings (a bit like a Mutas) and it is to be noted he has bomb bay doors on his chest.
If you can only do Destron that is fine but if you can do all the minions a good placement for the minions would be Deathwing perching on the shoulder with no cannon and Razortooth lurking at his side.