Wall paper no longer showing

Thanks for your reply.

I've tried using a new wallpaper from the different options available from using my own photos saved on my iMac to those those supplied by apple (still or dynamic options, the download for these seems to be happening ok) and it makes no difference I still have this grey screen.

What I have noticed so far it that the screen saver kicks in ok. it seems to be just the wallpaper that's the problem

Progress so far (or lack of)

I've tried using shut down and restart to see if my wallpaper will reappear but nothing.

What I have noticed using either shut down or restart the grey screen goes as the process starts and my wallpaper appears as the shut down or restart process continues.

The other thing I've found is that if I look at my time machine backups the grey screen disappears and my wallpaper is there but out of focus.

So it looks like my wallpaper is being loaded but is being covered up by this grey screen I'm getting.

I've looked in settings to see if anything can be changed but cannot find anything.

now I'm really confused, instead of shutting down my iMac last night I used the sleep function.

At this time the grey screen was still there, upon awakening my iMac this morning my wallpaper was back as it should be no sign of the grey screen that had been plaguing me.

What the problem was I guess I'll never know, I just hope it never comes back.