Hardshell Redux - COMPLETE, now with profile

I've decided to revisit my old fan character, Hardshell. He was one of my first repaints, years ago, and I loved the character. He was repainted from a red Bumblebee once I'd finally got hold of a yellow version, and was gloss black and gold.
Well, I found an old Bumblebee keyring with an arm missing, as well as a Cliffjumper, and decided to have another go at him. I took out Bumblebee's arms and trimmed down Cliffjumper's to fit. I also sculpted a faceplate onto 'Jumper's head and fitted that.
I opted to change the main colour to a really dark purple, which I thought would be a little more interesting.
I still need to do a couple of touch-ups, and I want to put some detail on te back of his head when I decide what. I was going to attach a Decepticon symbol, like the original Hardshell, but I thought that would be too garish given his stealthy tendencies, so I want to get some Reprolabels rubsigns when I can afford to.
Here goes - vehicle mode first:


Note the big black square at the back. Any suggestions on how to fill that?
Robot mode:

Here you should be able to see how I shaved the shoulders to fit Bumblebee's body.

Somehow the colour on this shot looks much more like the real-life colour. It is a very dark purple.
Well, I found an old Bumblebee keyring with an arm missing, as well as a Cliffjumper, and decided to have another go at him. I took out Bumblebee's arms and trimmed down Cliffjumper's to fit. I also sculpted a faceplate onto 'Jumper's head and fitted that.
I opted to change the main colour to a really dark purple, which I thought would be a little more interesting.
I still need to do a couple of touch-ups, and I want to put some detail on te back of his head when I decide what. I was going to attach a Decepticon symbol, like the original Hardshell, but I thought that would be too garish given his stealthy tendencies, so I want to get some Reprolabels rubsigns when I can afford to.
Here goes - vehicle mode first:


Note the big black square at the back. Any suggestions on how to fill that?
Robot mode:

Here you should be able to see how I shaved the shoulders to fit Bumblebee's body.

Somehow the colour on this shot looks much more like the real-life colour. It is a very dark purple.