I have thought of this in the past, It would really help cooling the liquid if the tubing had radiating fins to increase the surface area, Got the idea from a heating system we had when I lived in alaska, Our heating was by hot water that was pumped through copper pipe with radiator fins running the length, a lot of heat came off of that and the house stayed nice and toasty in the middle of the sub zero winter. I did find some on the net, might not be as good looking as polished smooth tubing but if you are going for a unique look, maybe a steam punk style and extra heat removal from the liquid, I think it would work.
Copper fin tube.
Spiral Fin Tube, is said to have a higher heat transfer due to its sharp twists making the fluid move and mix rather than just moving down a straight shaft.
Im sure you could get these in stainless, The site I was looking at was in Korea and I noticed they had even Titanium, but I did not look specifically for Stainless. Did not see prices either so I have no idea what this kind of stuff would set you back.
One thing I came across that you probably already know about, is that some people are able to get some tight loops and angles bent into the metal tubings by filling the tube with sand when bending, this is supposed to help keep the tube from kinking when bending, also the addition of heat helps.
If you go through with some metal tube please keep us updated, I did see one rig on the net not to long ago that used copper tubing and it came out really cool looking.
