Hi lucianus_luciferus, thanks for your feedback.

The cases should be smooth, the pattern that is seen in the photos is due to them being 3D printed.
Usually with most FDM 3D printers you can see the individual layers, thus why I mention that quality is the biggest issue with different colors.
White filament reflects light really well so its almost imperceptible, with red it becomes more noticeable and black is the hardest (at least in my experience).
The glossy finish is because the cases are being printed on glass, the sides of the case are opaque.

Nice thinking on the gold, actually I have some gold filament available, will definitely give it a shoot and report back.