Real Steel Robot Concept Art and Special Effects Featurette

Just a sample of some of the production concept art and robot character design done by Victor Martinez for the hit film. Via i09 which also has a great interview discussing the design process and inspirations...

One important way these robots are different from Transformers: they look like they were made by people. Martinez says the design team was keen for the robots to look utilitarian, with gears, pistons, servos and gyros. "They had to feel like they really functioned," he said.
Many of the robot designs include a throwback to the vintage, humanoid robots of the 1950s, with an "old-timey nostalgic feel" but also a contemporary spin, says Martinez. It was all part of establishing a "robot language" that would inform all the different robots in the movie.

Also check out this featurette from the Daily that covers the special effect used to create convincing fighting robots.