These pages use CSS style sheets, and if you read this line, then either your browser is really old, or it's weirdly configured... I did try to adjusts them in many aspects for old browsers, but it's such huge extra work, that I had to give up...
You only need this light JPG image.
You can right click...
Well you can just click on it first to see it, but then click the Back button on your browser,
and right click on this link and choose "Save target as",
and then save it in a folder on your disk and remember where you saved it.
Now, on Windows systems, click the Start button, then (or ">") Settings > Control Panel > Display > (choose the) Background (tab) > Browse (and here you browse to the folder where you saved it and select the image that you just saved) > Open.
Now you should be back at the Background tab.
You now maybe only need to check that the Picture Display (or Options) is: "Stretch" (select it, not "Tile" or "Center")
Now OK it.
No, there more. There is the story about this particular picture of the Sacred Heart of Jesus (from Father Bishop Roman Danylak's site).
But maybe you would prefer one of these desktop backgrounds:
another Heart of Jesus background
Heart of Mary
Our Lady with Infant Jesus
the Holy Family
another Holy Family background
Jesus' Holy Head crowned with thorns
Our Lady of Carmel
Our Lady the Ark of God
the great Pontifex Maximus John Paul II
Croatian Cardinal Alojzije Stepinac
Croatian general Ante Gotovina before Pope John Paul II
Croatian Priest Zlatko Sudac and Croatian general Ante Gotovina with Croatian difensors Tomo Ćavar (and if someone knows the other one, let me know... see "Contact" on top)