Thank you ! Sorry for the late reply, but I'm not around on dA anymore. Thanks for your support.
For the how to, it's basic photograph, really. Just focus and meter the light on the background, use a tripod, and wait the right moment !
It was difficult because there were lot of people coming in and out, and the place is really small.
The last important thing is the shutter speed. You have to set it at 1/4, or something like that.