You can post screenshots of unauthorized personal re-skins ... but to redistribute even freeware assets without explicit permission from the creator is illegal, especially if it is a payware asset.
Just a a Windows OS CD, a Norton AV CD ... etc ... A EULA applies to its ownership ... as if you bought a JR loco, you do not own it ... they still retain all the legal rights over the asset.
That called the "End Use Licence Agreement" ... you bought a licence to operate it ... and a license can be revoked by a creator/owner.
Hence, if you lent/gave away/sold/borrowed a Windows OS CD to a friend, Microsoft could turn your Windows OS off, and procecute.