Thanks for the input. Here are some sample images. It probably helps to see it to get a feel for it:
The images are nice, but they won't make a practical deck. You'd have better luck creating some kind of four-way fanning deck - the different fans could be the American Flag, a bald eagle, and any two other genuinely patriotic images you could think of. But even then, most non-Americans wouldn't buy it, and any American who isn't a dyed-in-the-wool patriot (or doesn't perform for dyed-in-the-wool patriots) would probably not be interested. Your market would be limited to mostly American patriotic flourishers - in other words, a small niche of a small niche.
If you wanted to continue with the patriotic "big flag" idea, here are some suggestions:
Perhaps a sky-blue background with white borders on the cards would work better. Unless you want this to be a novelty deck and nothing more, you need to have some kind of border on the front or the cards will be distinguishable from the edge of the deck stack. The edges need to be the same. And yes, the market is pretty much over most black decks these days - the only ones that are selling are ones with white borders, and even those aren't common. A border may ruin the perfect flag concept, but it would make these into real playing cards and not just rectangular puzzle pieces.
You need a two-way deck back, something that won't allow a person to flip a few cards around in the deck and immediately identify them face-down because of a one-way back pattern. One possible suggestion suited to the theme: four American flags, with the blue field in the outer corners of the card back and a white border around the square four-flag pattern.
There are many US/patriotic/flag themed decks already - most of them suck, and the ones that don't are simply not very attractive, interesting or well-made. You'd need to do some stellar artwork and design to make yours stand out enough to make people want to buy it. Merz67 (my least favorite deck designer) created a series of six red, white and blue decks, and USPC has a US Flag deck of their own - a flag-pattern back with some patriotic images on the front, all done at the quality level of Chinese-made Aviators (even Streamlines are better); not distinctive at all and not good for card games played by adults.
Worry about all of that first before you even consider a printer. Your idea isn't impossible, and done right could be a game-changing success, but you have an uphill climb ahead of you. You need to be creative and artistic while at the same time not making the deck impractical, kitschy or chintzy.