Upload to root/styles/*YourStyle*/xenforo/
Go To Admin CP/Styles/*YourTheme*/Style Properties/Node Icons/
Set your width and height to 36px
Go to Node Icon:Forum, set position to 0 0
Go to Node Icon: Unread Forum, set position to -36px 0
Also make sure both backgrounds are transparent for the node icons.
Save all changes and done!
Hope you enjoy these, and i can also make custom colors for you as well.
Right Click and Save As:
BTW if you use these, a simple thanks will be sufficient.