As said above, from a diameter point of view you are good upto 17" so long as they are not stupidly wide wheels.
Other things come into play when choosing wheels though. You need to consider:
->Wheel diamter - we covered this, just how tall a wheel is
->Wheel width (often referred to as j) - so 5.5j is a 5.5 inch wide rim, and 7j is 7 inches etc.
->PCD (bolt pattern) - bravo/a is 4x98 which most fiats are, pretty much all but some of the new ones are 4x100.
->ET or Offset - This is to do with where the mating surface of the wheel is in relation to the centre line of the wheel, cars all have different offset so you have to be careful you don't get wheels that will stick right out the arches (lower ET). A higher ET can be correct with spacers and longer bolts but a lower ET will just stick out further and thats that. This is assuming the wheels are same width, if they are not there is plenty of offset calculators online that will calculate the change in inner/outer clearance for you.
->Tyre size - clearly you can change tyres but you want to keep the rolling radius as close to stock as you can. Again, plenty of online calculators you can stick tyre sizes in and they tell you the differences in rolling radius in mm and & and how much taller the sidewall is etc etc.
But back to the wheels in the first post, these should go straight on no worries if thats what you want.