Christians Israelite's are taught not to have likenesses of anything God has made, eg. artificial plants or flowers, pictures of animals or people, etc. (read Exodus 20:4 and Deuteronomy 4:16-18).The reason for this is "lest ye corrupt yourselves" ie. lest we come to think more about man-made objects than about God and give honour to that which is created rather than to the Creator.
This includes likenesses on wallpapers, curtains, furnishings, dolls, clothes, accessories but toys or books for educational purposes are permitted.