But, only if they are turtles (programmable objects).  Yes, you can stamp an image on top of another stamped image, but you cannot then change their order afterward—because it has become a painting!

If you have more than one turtle on the page, you can move them infront or inback of one another.

For this, you will need to know how to talk to a particular turtle so that the correct one moves. See Talking to Specific Turtles.

To get the turtle named t1 in front of another turtle, type:

t1, infront

inback works the same way.