I have added some Custom Jabber Emoticons following the below pdf:
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/jabber/Windows/9_1/JABW_BK_CA48EE46_00_cisco-jabber-for-windows-administration/JABW_BK_CA48EE46_00_cisco-jabber-for-windows-administration_chapter_0110.pdf
They are working for me but some colleagues who added the custom emoticons folder can only see them really small.
The problem seems to be that in Windows 7 you need to change the below settings so emoticons show in real size:
Start Menu - Control Panel - Appearance and Personalization - Display
Change Display to Larger - 150%
Once you logout/logon the emoticons should show in their real size.
NOTE: It helps if your screen resolution is higher (my screen is at 2880x1620) as otherwise this change might make your windows desktop icons (or MS Outlook/Excel/Powerpoint views) too big.
The question would be if you can fix this in future versions so emoticons display their real size and this is not depending on the Windows 7 display settings.
Many Thanks