High Sierra desktop picture on waking

Hi folk. I upgraded from El Capitan straight to High Sierra. On both my iMac and MacBook Air I find that when I wake the computer, the fuzzy desktop picture that snaps into focus after you log in is always the same (I think it's the picture you have on Desktop 1), regardless of the last desktop you were using when you last logged off. In El Capitan, when you wake the computer, it shows the picture from the last desktop you were using. In other words, you can have a nice variety: one day you'll be greeted by a picture that is predominantly green; another day by a picture that is predominantly red, for example. Now, with High Sierra, this doesn't happen; it doesn't change. Is this purposeful on Apple's part, or is there a tweak I should be making? I know this seems unimportant, but what first attracted me to the Mac was its appearance. It matters to me.

Thanks in advance.