So I've already done some "work" on Masque support and here's what I've done:

• 239ac14
  Adds general Masque support, works fine except that the empty bag slot has a default backdrop.

Now to temporarily fix that in ItemButton.lua on line 288:

function buttonProto:Update()
	if not self:CanUpdate() then return end
	local icon = self.IconTexture
	if self.texture then
		icon:SetTexture(self.texture)
		icon:SetTexCoord(0,1,0,1)
	else
		icon:SetTexture([[Interface\BUTTONS\UI-EmptySlot]])
		icon:SetTexCoord(12/64, 51/64, 12/64, 51/64)
	end

Change this:
icon:SetTexture([[Interface\BUTTONS\UI-EmptySlot]])

To something like this (depending on the Masque skin, pretty sure this would be dynamically doable?)
icon:SetTexture([[Interface\AddOns\Masque_Caith\Textures\Backdrop-Item]])

The only thing I haven't gotten working is the pushed effect but I'm sometimes terribad at this.

Would be nice if you could add Masque support, if not just close the issue.

Thanks!

Yes, Masque support would be very nice.

Has anyone managed to get Masque to work properly after patch 9.0? I can get it working with the old code modifications except the quality borders are broken.

Hello,
Facing the same issue, all my items have a "goldish" quality border