Thanks to Only a Hobo for pointing out that the skins were not available on the new website.
We’ve taken advantage of our mistake to now put them on a more convenient url (along with the frostwire installers) on dl.frostwire.com
You can now download the FrostWire skins for 4.13.x and 4.17.x at
http://dl.frostwire.com/skins
Official FrostWire Blog 
What about frostwire 4.18.0
yeah what about the new version??
yeah i agree!! what about the new version?4.18.0???