I think it'd be just logical if a group game could have a thumbnail or trailer video paid for with group funds.
Nothing like audio, since audio can be used anywhere and some people might extort robux from their groups just to upload audio for free.
Roblox already added this feature where you can even put people on a pay roll and take out money from group funds, but it is currently down for maintenance and will be back up on Monday. Check out more on this Roblox Blog post: http://blog.roblox.com/2015/05/share-the-wealth-with-group-owned-games/
Exactly: You can take money out yourself from the group funds, then pay for the thumbnails with the money you took out. I know it's not perfect, but before you couldn't even use group funds to buy thumbnails at all.