Missing files?

I think you are correct when you say it's a bug in one of the web pages. I found another .png file on the NAS with a similar name, copied it into /frontview/dashboard/images/scroller/ directory, amended the ownerships and permissions and now I don't get the error messages. I also can't see any change in the admin index webpage, which is where they're loaded when it's displayed on login. If someone can supply me with the correct files, or tell me where to get them, and what difference it'll make, then I'll install them. Otherwise I think I'm done here.

Thank you again for all your prompt help, very much appreciated.