--The wall of your room doesn't look nice.&

问题补充：

-- Thewallofyourroomdoesn'tlooknice.-- IwishI___itgreen.A.shouldn't have paintedB.wouldn't paintedC.hadn't paintedD.don't paint

答案：

C解析wish后面接从句用虚拟语气，这里表示与过去事实相反，所以选C。