I have 16 teles on my Spider coz I prefer them to the standard pepper pots. I would prefer 17s but don't think the 16s look too bad. I did put 10mm hubcentric spacers on the rear as the offset seems to be smaller and they are too far inset in the arches without. I don't seem to notice it on the front though.
I had the 16" tele's on a phase 1 a few years ago. I had problems with them clipping the rear suspension when cornering hard because the wheels sit that much closer to the body (offset of 40mm IIRC). Spacers are needed really (as Wheelnut says).
As wheelnut's picture shows they look fine, will give a softer more comfortable ride over 17"( 156 16" Teles run 205/55...GTV 16s run 205/50, 17s run 225/45), are much cheaper to buy.....including the tyres when needed.
I'd fit with 15mm hubcentric spacers front & rear. The 'clipping' of the inner suspension mentioned earlier was probably a wheel weight rather than the rim itself, spacing will cure this & fill the arches outwards better.
Wheelnut has cheated slightly by parking on grass hiding the tyre sidewall height!
It is, though, a lovely photo - what a great colour - really suits the Spider's design period. Metallic red (Proteo) is the same era but I like that green more - the red is similar to a BMW colour (Calypsorot) whereas the green is more unusual.
Also, Wheelnut, can you please confirm the tyre size - 205/50 16 as Clive said for the GTV? They definitely look lower-profile than the tyres I've seen on 156s.
My Spider's on 17s and I agree with Clive that 16s give a nicer ride (and are a lot more common/cheaper to find) - my last Spider had 16s and seemed to soak up small ripples/rough surfaces better. The weight of the wheel/tyre combo is important too. Less unsprung weight=better ride in my opinion.
At the end of the day though, the best wheels are the ones in good condition. Changing wheel size can be quite a cost if you have to fork out for four new tyres - the used tyres, even if nearly new, tend not to recover their cost if you try and sell.
Also bear in mind that new tyres of good quality will also have improved smoothness compared to old tyres. My Spider has two old (original version) Eagle F1s on the back, and the noise/roughness made me think a wheel bearing had failed (I've checked the bearings and they're fine). I understand that new Eagle F1s have been improved but even so, just a warning that tyres can make a difference as well. Confusing!