Anyone who has been a part of the Transformer phenominon in their life knows that on of the Highlights of the Tranformers cartoon is when the Insecticons flew in.
My Idea is:
Don't make them so big. The Insecticons were pretty big in the cartoon. I say, make them small. The size of the tranformer Cell Phone in the first movie. But make hoards of them. It would be cool to see a swarm of Insecticons. The sky goes black! The insecticons block out the sun. Then swoop in for an attack!