When creating launchers and selecting custom icons, the custom icons no longer display. More info is available at this forum thread: https://forum.xfce.org/viewtopic.php?pid=46266.
There is a workaround, but using the GUI method of selecting a custom icon no longer works.
Please make sure cropped icons properly work with the panel in vertical mode.
The icon is now scaled to a square, so it is HUGE in vertical mode.
@ToZ: Could you check whether this is still the case with 4.13.2?
I've tried to address this problem, specifically in https://git.xfce.org/xfce/xfce4-panel/commit/?id=6345387b168fd25240b1d025e277fb0ea4c7131e
Yes, it works now. Thanks for the fix.