This is purely cosmetic. There is an open Jira ticket that will hopefully address this. In QUINC 7.4 there are two icon files that are missing in the Image recognition categories, namely: Grenade and Aeroplan (sic Aeroplane).
As seen below the icon files for both Grenade and Aeroplan is not available
Steps below just on how to fix it till the software fix is permanent in future loads.
1) Copy the two file attached to the KB (below) onto the QUINC Server into the folder path below
C:\Program Files\AccessData\Forensic Tools\7.4\bin\app\images
2) Go back to the Investigator login screen where the cases are listed. Open up a case that has had image categorisation run on it, scroll down to the Image recognition tile at the bottom of the case overview