For Mac Owners:
1) Click on the link under the picture of your choice (2 choices are proposed according to your screen resolution).
2) Then click on the expanded picture and at the same time press the Ctrl button.
3)

Select the option "Save picture on disk" and choose a file to save the picture. If your Mac is more recent, you may have the additional option "Set As Desktop Background...". In that case, choose this option and do not pay attention to the following steps below.

4)

Then click on the apple on your task bar.

5)

Select Control panel and then Appearance.

6)

In the Desktop tab, click on the Delete picture button and then on Place a picture..., and select the image that you have just saved.

7)

And there you have it!