HI Benoit, The contour graphs can either be matrix or vector for the X,Y but the Z needs to be a matrix based on its values for the corresponding X,Y Pair. I made a quick example of each method below I hope it shows what I mean.
You can replace individual elements of controls with GIFs too. I once replaced the pointer in a horizontal point slide with an animated GIF to make a custom progress bar. In my application I opted for a GIF of two turtles engaging in sexual congress.