Design Requirements
Requirements for Pixel Designs
PNG, JPG, BMP, or GIF file format.
Maximum file size 10 MB.
Image resolution at least 200 dpi for apparel.
Image resolution at least 400 dpi for non-apparel.
Maximum size 4000 x 4000 pixels.
Minimum size 1000 x 1000 pixels.
Design is isolated.
More design info here
