Welcome to the site!
Always liked the look of the bigger rims on the libertys like on your Jet edition, but always wondered why anybody would want a jeep with 20" rims and low profile tires.. though in my opinion the KK doesn't fit the appearance of one.
That being said, 16 or 17 rims would likely be based on your preference and price range.. as well as the overall availability of the ones you prefer. But essentially, it would all depend on what you're looking for. You said you don't go offroad, so I'd imagine you're probably looking for comfortability and better traction in the snow..
if you're still sitting stock, you can find plenty of advice and informaton on what tires and rims will fit, by looking through the Tires/Wheels Section in the KK Section..
IIRC, KK's came with 16s on some models so you should have no problem going it a 16 or 17 inch rims..
But if it's opinion rather than information that you're looking for, myself I would go with a set of 16 inch x 7 inch rims with 235/70/16s wrapping them up.. that way your back spacing would be factory and you wouldn't have to worry about rubbing.
I could be incorrect, but I believe with stock suspension if you bump up to 245 you'll rub somewhere thought not too badly..and if that's the case, I'd stick in the range previously mentioned.
Could probably find a set of stock rims pretty cheap at your local boneyard, or on a forsale forum.
Or find a set that fits on craigslist or somewhere.. as I said before, all depends on what you're looking for, price range, and availability.
Best of luck and hope somebody can chime in with the answer you're looking for.
