Came across this issue after setting up a Mac using the OS High Sierra. There was a delay in showing saved files and screenshots on the Desktop. Searched for a fix and came across this solution which worked for me. Hope this helps!

Go to the Apple menu at the top left of your screen and select System Preferences. Then choose the iCloud panel within System Preferences and click Sign Out. In my case, I chose to save a copy of the files. Then sign back in. This was an immediate fix without having to restart the computer.