Severity icons on the Event Management dashboard will be broken with a broken image and a big square box.
Missing "image_admin" role for users who can access the Event Management dashboard.
By default OOB, "image_admin" is inherited from "evt_mgmt_user" role but in somecases users delete "image_admin" role from the "evt_mgmt_user" role.
Add "image_admin" to the user or to the contains sections of the "evt_mgmt_user"role.
The severity icons on the dashboard are coming from "sa_contextual_colors_and_icons" table and in the table open any record, let's say warning severity and there are 3 sections in the form view, but for the user without the "image_admin" role, we cannot see the records under icons sections.