<b>Header:</b>
0x00 (word) - X start of the art
0x02 (word) - X end of the art (shifted right by 2, substracted by one) - x2=(end>>2)-1
0x04 (word) - Y start
0x06 (word) - Y end

Now, until the counter reaches the final line, the following is looped:
Header:
0x00 (byte) - X start of the line
0x01 (byte) - length of the line (shifted right by 2)
0x02 (word) - line number

After that, there are bytes. Each byte corresponds to one pixel. The SH2 code adds $13 (or something different, depending on the need) to each byte. That final value points to a CRAM color. Simple as that.

The art should end with a 0x0000 at an even address.