In general, no. Our system supports only credit card payments at this time.
However, if you have a client that pays for their order offline before they place their order through the site, one possible solution might be to create a coupon code for them that's worth whatever value they previously paid you, and then have them check out using that code. This process would allow your clients to select their images and place their order through your storefront (using their coupon code) without having to provide any additional payment information on the site.