For the casing I know the big trend is to use a 3D printer but not owning one I had to improvise. I use a simple black PVC case that can be founded in any electronic store and simply cut the opening for DC Jack connector and the RGB connector.
You should maybe finish assembling the board and then go with your finish board to the shop to find a matching case.
I also had to cut an opening to let the wifi antenna protrude from the box (not that I believe it will improve the signal, I had simply forget about it when I bought this case!).
So here are a few photo to give you an idea of what it look like:
It’s not the best one can achieve but it will go behind my TV so aesthetics was not a main concern for this one.