need help to get my python image to move around using tkinter

[twgrops at googlemail.com]

Hi I am new here and to python,

I am currently studying towards my degree in computer science and have to build a program but I have hit a brick wall. I am trying to make an image move around the canvas. I can make a rectangle move using the following:

#test rectangle
id1=canvas.create_rectangle(3,7,3+10,7+10)

# Generate x and y coordinates for 500 timesteps
for t in range(1, 500):

    x1,y1,x2,y2=canvas.coords(id1)

    # If a boundary has been crossed, reverse the direction
    if x1 >= x_max:
         vx = -10.0
    if y1 <= y_min:
         vy = 5.0
    if y2 >= y_max:
         vy = -5.0
    if x1 <= x_min:
         vx = 10.0

    # Reposition the robot
    canvas.coords(id1,x1+vx,y1+vy,x2+vx,y2+vy)
    canvas.update()

    # Pause for 0.1 seconds, then delete the image
    time.sleep(0.1)

However i would like my image/sprite to move around:

objecttank=canvas.create_image(950,650,image=gif6, anchor= NW)

from what i gather it is because an image only has two axis, x and y but the rectangle seems to have 4 values, my error code keeps saying expecting 4 but got 2. 

Can anyone help me in the right direction, many thanks tom.