You can also install your own icons directly into Tasker's icon directory /sdcard/Tasker/.icn/. Make sure the icons are in a subdirectory. The subdirectory should also only be one level deep (no subsubdirectories).
Icons must be in PNG format.
Example: a two-icon set called Christmas would have the two files in these locations: /sdcard/Tasker/.icn/Christmas/santa.png