As a side note One actually does not have to kiss a Siddur when dropping it is also minhag.
While you are correct that they are not on the same level of devarim shel kedusha as Tefillin.RE:, Halachos of putting tzitzis out for disposal the ideal way to dispose of them is in shaimos, also tztzis are not allowed to be defaced to get rid of them.Does this not signify that they are to be treated with respect.
Would you put a secular item on on the covering of a Bima in a Shule? Imagine a big Yankee logo on or a barney just to intrigue kids.
How can a person justify putting sports teams and cartoon characters (who as I mentioned above are also portrayed in christmas shows) on something used for a Tzivui. when we say the Bracha Asher Kidashanu that which is made holy should mean something when putting on the Tzitzis.
RE Yarmulka as mentioned above it signifies fear of G-d and keeping in mind that which is above you, elevating yourself wherever you go. More importantly it identifies you as a Jew, by secularizing it you are belittling it and taking away its purpose.
And while there might not be a chiyuv you are defintly now causing a Bizayon to something used in a Mitzva as it reminds a person about Anochi Hashem Elokecha and uvichukosiechem Lo sailaichu
How many Jews risked severe beatings just so they could wear one. A choshuve Rov told me that he will never forget the beating my grandfather got from a Nazi for wearing one.
putting cartoon characters and sport teams is not exactly a tiferes.
I would also note While many poskim do not agree, there are poskim that do in fact say wearing a yalmuka is Halacha. (even though there are certain Heterim)The ones that do not hold it is Halacha say that it is midas chasidus.
This is more then se past nisht.You can say se past nisht about wearing what might be inappropriate clothing but belittling what is an ID tag of a Jew and that which is meant to signify what is above you and keep you from Aveioros is a bizayon of the Middas Chassidus or Halacha.
As I said above Just because an item was designed by a Jew and is in a Jewish owned store does not mean it is correct.