Here is how to make Dynamics display custom icons to add polish to user experience.
Icon schema name format:
Replace # with the value of CaseOriginCode picklist item.
Note that the prefix must be new_.
Setting the display icon can seem like a minor thing, however it does add polish to user experience.
Check out technet article https://technet.microsoft.com/en-us/library/dn660975.aspx.
Cheers – Sy