Titan Wars Fantastic work
But as others have stated, the five limb structure (or the structure that APPEARS to have five limbs) really doesn't work on a humanoid basis.
If you look at the "shivans" from the video game FreeSpace, they're five-limbed aliens with a totally different biology, and it works great. By giving something humanoid five arms, it's very difficult to understand the image. I get a sense of incredible size, power and machinery but absolutely no understanding of how it's meant to look.
It confuses the eye, and that's a real pity.
New Land 
Graveyard Shift