I finished designing the backplate for the 7" LCD from adafruit. It has ears to secure it to the rest of the system. I added reinforcement to make it stiffer, and a cutout for the cable ribbon.

There are standoffs for the LCD's electronic circuit, and standoffs to secure a Raspberry Pi, model A+ or B+.

Here is a rendering of this part :

The green block on the left is the LCD driver, and the lighter green block on the right is a Raspberry pi B+. The blue block beneath is the LCD.

The 6 fixation ears have 3mm holes, to secure it on another part. The plan is to have a border around the LCD on this other part, so it can't move laterally. Then this plate screws onto it, locking it on a vertical axis, causing it to be fixed. Had the LCD had mounting tabs, i would have been able to make a simpler design. But here it is, and i'll print one tomorrow.

I'll design a complementary part in order to enclose this screen so that it can be used on it's own. I'll also design a thicker part to also enclose the raspberry opi, and then multiple parts for the console.