Rod,
In theory, the only way you can avoid the Gigabit Ethernet network bottlenecking in one OC-12c pipe, is to aggregate two OC-12c connections. Gigabit Ethernet-to-ATM bridging should be able to accomplish the load balancing; I have done this with another vendor's switches, but I have no experience doing it with Cisco's 6509. (Even then, I don't think that customer ever actually generated a whole OC-12 pipe's worth of traffic at any given time, though both OC-12's were active.)
I guess it also depends what you're connecting to: some GigE ports get throttled down to around 600Mbps bandwidth by the hardware, to interface better with OC-12c. The only way to get full-duplex GigE speed I think is to point it into an OC-48c. I've done this with a Cisco ONS 15454; but this customer was being capped at 300Mbps feeding into the GigE by their Internet2 provider.
Do you have any other choices besides an OC-12, like dark fiber, or a GigE-based or WDM-based service provider? What kind of pictures are you moving, and how is it getting done now?
I built a GigE network over dark fiber for a health care system two years ago, that moved a lot of X-ray images from four hospitals across the fiber to a central storage area. The systems doing the X-rays had no better than Fast Ethernet connectivity, so we never ran out of bandwidth on the GigE backbone. I think that even with a Gigabit Ethernet NIC in a machine, you're not going to pump more than 400 to 600Mbps out of it, tops.
Hope this helps.
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