If you made up the martial arts style then of course you can wear it. If not, you usually wear the mon of the family whose style you practice. In Asia it is not about you. To think that way is rude and selfish and does not serve society or the family whose mon you are wearing as a whole. Wearing the mon is literally a sign that you have been adopted into the family and therefore are now allowed to learn the family martial arts style. Credit always goes to the teacher not you another reason not to wear your own crest.

The family martial arts style traditionally was not taught outside of the family and it was also not taught to girls as girls would marry and leave the family to live with their husbands family. To take knowledge of the family martial arts into another family could mean the end to a clan if someone outside the family knew the way they fought, because if you know how someone fights it can be defeated.

Mon (japanese family crest) are usally worn on a kimono or kendo gi when training iaido or kenjutsu.

My family has a crest or emblem if you will depicting a knight riding on a lion so my question is if im allowed to wear my family crest on my kendo gi even though im not japanese (im european by the way).