I have a hard time looking for this cover. It's Optimus Prime looking down as a silhouette worms eye view that shows which makes his feet look huge!!! Plus there isn't a background, I think it's a sunset gradation.

 

This? All Hail Megatron 9B.

 

No I don't believe it was produced by IDW.

 

Huge feet? Sounds like Pat Lee art!

Well these come to mind:





Not Pat Lee, but worm's eye view and huge feet:

 

Can't see anything from Marvel US like that, maybe it's the Pat Lee stuff above.

 

This? Although it was never actually released it was solicited Generation One Vol 3 issue 12B