Sorry for the pics, it's kinda not pretty but best I could manage with what I had around:
Here's 1 pic with the phone on the dock : took picture with 3GS's phone, quality is shitty, will try to get more later:
Others photos have been made with Gnex's with flash:
I've been using regular boards pins : used some scissors to reduce their width (did that randomly until it was fitting inside the lego bricks).
Then used a hammer to make two holes on top of a lego brick, evaluated where holes have to be only with eyes. First brick was a fail and gap between pins was too wide, 2nd try was good.
Linked the 2 wires from a wall charger to the pins (need to attach 'em more seriously (with some duct tape) as it's only wrapped around atm).
Then tested and it's charging instantly... (info on phone show that it's "usb charging")
Will probably add some floor so it'll maintains pins in position even if I move around the dock