It should look like the player who put it...
if u wannabe sure that a NPC only works for the player who put it down u could use some "paramters"
so for example the playersid. Just set the playerid as the image file of the NPC and read it out with #f . normally online the server adds an .gif to the filename but with #e you can substract it. With that id u can check for the right player...