No. It is not allowed.

Quote from shakejunt :

hello can someone upload this skin i made please, you can make it better if you want to

Hiya, you don't need to have a S1/S2 licence to upload skins. Go to your LFS Desktop (LFSWorld) and open "My online car skins". Near the top right corner there should be an option to "increase" the number of available slots. You should be able to buy 50-skin slots for just £1 (payable via paypal too!)