Replica kit is a good try-on category. The garments are simple in cut, the colourways are bold and high-contrast, and the buying question is often "does this fit the way I want it to" rather than anything subtle about drape.
There is one honest problem, and it is worth putting up front.
Text is the weak point
Image models are bad at text. A player name, a squad number, a sponsor wordmark: expect an approximation, frequently a wrong one, sometimes a convincingly wrong one. This is a known property of the technology and not something a prompt fixes.
For a category whose main upsell is printing a name on the back, that matters. Do not put a generated image next to a personalisation flow in a way that implies it previews the print. Show the shirt with try-on; show the personalisation with your existing mockup tool.
What works well
Base kit, colourway, crest position, sleeve length and overall fit read reliably. Home and away variants are visually distinct in exactly the way generation handles best. Fans buying a size up or down for a particular fit get a real answer.
Kit sets
Shirt, shorts and socks compose in a single generation for one credit, up to six pieces. For replica kit that is a natural bundle and a better basket than a shirt alone.
Licensing is your side of the line
You are supplying the product images and you are responsible for having the rights to them. Generated results are derived from what you send. Club and league licensing terms vary and some restrict derived imagery — that is a question for your licensor, and the terms put it on your side.