I found the Lego case I built for the O.G. Raspberry Pi Model B back in 2012.
Even moreso than later versions, cable management was terrible in the V1 Pi. My idea with this was mostly to use built-in legs for cable management (just thread the cables through the legs to have them all go in any direction you wanted). Also, the original dimensions were remarkably well-suited to Lego cases, since the bricks are based on 8mm footprints. Got the board to just press-fit into the case very snugly. The only real trip-up was that this resulted in a case with an odd number of studs in length/width.
It has flip-up panels for the camera/display ribbon connectors, and a transparent slope piece to redirect the status lights out to the side like a low-tech light guide. Also, I tried to include a little bit of interior isolation under the roof to kind of guide heat out through the top vents. But I didn't build in any provisions for the I/O header.
In practice, my standard HDMI cables were a little too girthy and the bend radius too unforgiving to use the legs-as-management idea very effectively. Only those noodle-thin cables would have worked in arbitrary orientations.
"Front" with (full-size!) SD card access closed and open, and USB micro-B power input.
(Pretty sure Lego stopped making that style of hinge before I built this case. Many of the pieces in this were already more than 20 years old.)
Analog A/V side with Composite Video Out, 3.5mm audio jack, and the transparent status light guide.
The back, with the 10Mb Ethernet and 2 USB 2.0 ports.
The HDMI Out side. It was difficult to try and make this a small as possible and still fit most HDMI plugs.
The top with Camera and Display connector panels open.
The inside with the top section removed.
And empty, showing the small number of spare tiles I used to keep the board raised enough for the SD card reader slot to be relatively level.
Haven't tried to build a Lego case for the newer boards. The dimensions are no longer as nicely compatible with the 8mm footprint of a Lego brick.