Reference: al-Muntaqaa min Fataawa Fadheelatush-Shaykh Saalih Ibn Fowzaan – Volume 3, Page 339, Fatwa No. 505
Question: What is the ruling regarding pictures and drawings on children’s clothing, since these [children’s] clothes are not free from pictures?
Response: It is not permissible to buy clothing upon which pictures and drawings of that which has a soul from amongst the humans, animals or birds. This is because making pictures and using them is haraam, for the many authentic ahaadeeth which forbid this and threaten severe punishment over it. The Prophet (sal-Allaahu ‘alayhi wa sallam) cursed those who made pictures [Saheeh al-Bukhaaree, volume 7 hadeeth 67] and informed that they will be the most severely punished on the Day of Jugdement [Saheeh al-Bukhaaree, volume 7 hadeeth 64 and 65]. So it is not permissible to wear clothing upon which is a picture and nor is it permissible to dress a young child with it. That which is obligatory is to purchase clothing without pictures and these are many.
And all Praise is for Allaah.