I'm a pro Designer/Illustrator/Photographer/Web Designer and I'd love to create a suite of 2-3 epic designs for just such a purpose...with a few caveats:
A - Too many cooks spoil the broth: in my experience the creativity of a concept is often diluted in direct proportion to the number of people who need to veto the design. The review process would be kept out of the forums for this reason - two or three staffers would be the panel - that's it.
B - The Brief: Valuable time would be spent on rough sketches and ideas before committing to production drafts. This is because full production illustrations/art can take over a week per piece (for complex designs) to complete.
C - The Cost: As this is my day job I'm not about to push paying work aside to commit a week (or three) to design a suite of two or three shirts/hoodies etc just for 'fun'... or because 'it would be epic man'. If the garment retailed for $30 ea I'd be looking for a sizable chunk of the profit margin. Even if we sold 100 shirts I'd probably still not even come close to my normal fee but there is a component of 'supporting the server' so that's OK (I normally get anywhere between $500 and $2500 per garment depending on the number of sides and complexity).
D - Shipping. CustomInk.com is OK for USA & Canadia
but we'll need a solution for those in the rest of the planet.