Beware! Grande Punto wheels are 100, rather than 98x4; and therefore need wobble bolts.
Personally, I wouldn't go above 15" on a Mk2 Punto -- although people have gone up to 17"... -- because of the strain it places on components (inlcuding the gearbox) that really weren't designed for them.
I know a lot of us have gone for 15" Sporting alloys: and so they may be seen to be quite 'common' -- but they do suit the car. Have a look through the Mk2 and Mk2b Punto Members Motors threads, though; and see what others have gone for -- 'twill give you a good idea of what looks right (to you), and what doesn't....