These are really awesome. I like the very select use of color. The detail work is amazing but it did take me a minute to figure out what I was looking at. It would have been nice if you used the brightest/most saturated colors to help visual clues (like their optics) pop more.
Omg, yes! Transformers! Nice choice of colors. Really like how it represents them both. I also really like the small text of their names on the bottom. Is that an existing font or did you alter it as well to match the piece?