The first capture group shall be a format. The currently recognized formats are `gb` and `raw`, though any format can be used. A program SHOULD gracefully report and exit on an unknown or unsupported format. The identifier of a format may not include a hyphen (dash).
Upon receiving a message containing the part, a compliant client MAY take steps to attempt a conversion to PNG or similar, or display the image inline. A thread with timeout CAN and SHOULD be used.
While there is no theoretical limit to the size of the image you can send, you are bound by any message length limits your server sets, as the entire part MUST fit in one message.