tajima makes the best machines. the largest tajima i have seen had 30 heads. it can be seen here:
Tajima Embroidery Machines - TFGN-930
the machines are run by a digitized tape roll. it looks alot like a miniature scroll for a "player piano". the skill of the person who "digitizes the art" is of great importance for two reasons
1) to replicate the art as closely as possible
2) to instruct the machine in the most efficient way to minimize number of stitches and thread breakage during stitching