"Looks" are always a matter of taste; but as other's have said, it's your car. IMHO; the 'Big Cats' look a little awkward with TT's on them.... if the car was a 429CJ car, I could "see" it better, especially if the spokes were polished as opposed to painted. (What can I say, Mitch's signature picture makes me drool a little!)
As far as alluding to some power under the hood; I'd look to something like the 17" 10-spoke Shelby wheels that Don has in his catalog. Those are very cool rims; and don't look "puffed up" like some of the other mfgr's that grow larger diameter versions of the classic 15's. The picture of them in the catalog shows that they look pretty doggone good; and I've seen in person a set of those wheels in 16" on the car that Bill B and his son put together for the son to drive. Between the polish job and twice as many spokes as a TT; they just exude "CLASSY Power".
One other choice that sticks out in my mind will probably invite some flames; but Imagonna put it out there..... I'm looking at putting bigger brakes up front on my '73 (once she's driveable again) as well as swapping out the rear drums for discs. The brakes I want to use ('94-'04 Mustang Cobra pieces) require 17" wheels for caliper clearance, and will require more backspace to keep the tires inside the fenders. Looking at the 2005 - 2008 Mustang "Premium V6" rims, which look like a different $helby-style wheel. Slightly different spoke design, and less "shiny".
I know, "factory discs and drums work just fine"; but a couple of years ago I changed out the brakes on a friend's '95 Ranger. 30 minutes to swap out the front pads and scuff up the rotors with a Scotchbrite pad on my cordless drill. 3 hours on the rear drums, part of which was spent staunching the blood from my broken nose. Yeah, brake-spring pliers snapped off at the pivot on the second wheel, had to switch to needlenose vice-grips; I was hunched over the brake assembly, vice-grips slipped on the very last spring, hands and vice-grips flew up into my face, and I looked like the loser in a bar fight.
I really don't want to work on drum brakes anymore.... take 'em off and 86 'em and don't look back. Plus, as I'm getting older, I'm seeing how many late-model cars are getting more "Performance Oriented"; while their younger drivers' skills are becoming LESS performance oriented! Bigger brakes will haul the old girl down to a stop more quickly, which is very good from the "Don't be the last car in an accident" standpoint. But 'bigger brakes' mean bigger wheels. Furthermore, comparatively there aren't that many really good tires being offered in 14" or 15" sizes anymore. You won't see me "pimpin' 24's" with rubber-bands for tires, but I could do 17's in the desire for better brakes and rubber.