you swear you want criticism? hahaha
I do not know what kind of criticism I could give this picture because for me is perfect.
Gotta have a good vision of metal, for a painting, and I do not think that should change many things. But if we want to improve and do something more realistic, I would say to get a picture of some real metal, extend the maximum and try to remake the same type in a painting. For example, some portions brighter actually placing a blank in a soft brush, to make a reflex light. Some parts could have this and other slightly more black, gray and not only causing a shadow reflected mainly in the spaces in which parts are very close, as is two parallel mirrors.
The proportions are excellent, as is the play of color and light, however, the light is coming from above, I do not know if the background was supposed to be just random or if it should merge with the picture, if that is the case, I imagine that the shadow is in the wrong place. The shadow of the rider should be on the other side, in front of him and not the back where the light is coming.
I hope I was helpful =]