Specific wedding customs:
“Mr. and Mrs. …. ” as referring to the hasan/kallah is clearly non-Jewish, as traditionally Jewish women did not change their names on marriage (prior to use of surnames, which were for the most part adopted by Ashkenazim in the 19th century)
Entrance ceremony – Jews had the hasan and kallah walk to the huppah with their parents, anything else is non-Jewish. Among goyim, the hasan arrives with his friends led by the “Best man”, whereas the bride is escorted by the father or senior male relative who has to “give her away” (Jewish give make their own marriage arrangments, at least in theory, so there is no guardian to give her way).
Post-wedding. Goyim traditionally leave town immediately after the wedding for a honey moon, so anything we do after our weddings (where the couple stays in town and goes to parties for a week) is Jewish.
As to what is a “custom” one should remember that customs, by definition, are constantly changing. New Jewish customs are constantly being created based on how we adapt halacha to changing circumstance. For example, 200 years ago there were no microphones or loudspeaker, nor any possible recorded music – and there were no photographers at weddings- Clothing constantly changes since new fabrics become available and styles change (e.g. no one wore pants 500 years ago) – the halacha for clothes pertain to the tallis katan and the need for modesty – the rest it how the Yidden adapt.