Elmo and barney are cartoon characters that you are putting on Devarim Shel Kedusha.(btw They also have christmas episodes and on sesame street they are very open to alternative lifestyles) This is not Chinuch, it is warped. If you feel that you need to entice a child by putting graphics on Tzitzis, at least let it be depicting a Mitzva. In terms of logos on Yarmulkes regardless of age, A yarmulke is a Yerie Malka. TV shows are highly improper, and sports teams for the most part don’t have the greatest role models. A Yarmullka signifies Hashem is above you and to fear him I do not understand where sports team logos cartoon characters etc.. fit in. It is a Bizayon that any secular topic should be on a Yarmulke
If you want to put a Jewish name (whether in english or hebrew) that is Kadosh, quoting pasukim or scenes depicting mitzvas are Kadosh. Flowers and nice sequined designs for kids are beautification.
Just because an item was designed by a Jew and is in a Jewish owned store does not mean it is correct.