In 1.13 you can place item frames on top of a block, but even though carpets are not a solid blocks if you atempt to place a carpet on top of an item frame, it pops up. 

Allowing carpets to be placed on top of an item frame could be a really neat feature since they only show the item placed inside of it when you place a carpet on it. That would be a nice way to create a dinner table. 

Thanks for your hard work guys!