How do I put a watermark behind plotted data using matplotlib

I found this tutorial on how to do a watermark but I cannot figure out how to put it behind my plotted data. https://www.tutorialspoint.com/how-to-plot-a-watermark-image-in-matplotlib

Changing zorder has no impact because I think it is being drawn on the entire figure. I would like to have a subdued logo behind my data which is always centered in the figure so I don't really want to plot an image as a data point because then it would move as it is panned/zoomed.

Solution

Setting the zorder to a negative value works for me. However, you also need to make the facecolor of the axes transparent:

import numpy as np
import matplotlib.cbook as cbook
import matplotlib.image as image
import matplotlib.pyplot as plt

with cbook.get_sample_data('logo2.png') as file:
   im = image.imread(file)

fig, ax = plt.subplots()

fig.figimage(im, 10, 10, zorder=-1, alpha=.5)
ax.plot(np.sin(10 * np.linspace(0, 1)), '-o', ms=20,
         alpha=0.7, mfc='orange')
ax.set_facecolor('none')

plt.show()