When Dr. Monica Ulterro is conducting an autopsy on Diavolo, there seems to be a collection of soup ladles shown in the background of the mortuary. I'm not very well-versed in morticians and their tools, but it would certainly seem odd to have those 3 tools.
Here's a closer look at them.
Considering that these tools are not present in the equivalent manga panels I'm going to assume that they're not supposed to be there.
I'm going to say it's a minor animation error and nothing more.
Based on the screenshots you provided I think it's very possible that the background was CGI. The sharp shadows, lack of detail, and flat colors and lighting all seem to support this. So it's very possible that they simply had a 3D asset that looked about right and used it.
