Three files available for download:

PhotoShop CS File - printready-octagontshirt.psd
Photoshop doc saved in CMYK 600 dpi with layers (fonts are rasterized)

TIFF File - printready-octagontshirt.tif
TIFF File saved in CMYK 600 dpi with layers (fonts are rasterized)

HUGE GIGANTIC JPEG File - octagontshirthuge.jpg
JPEG is here just in case. It's also in 600 dpi, but is RGB. And, of course, no transparency.