Hi Chik - and welcome!
I don't think there's any problem writing on Celtic jewelry for your site. There is overlap among a lot of the sites. I think Celtic ornamentation is important to the Scottish culture, and it makes sense.
Interestingly (to me anyway) my husband, who is of Irish and English descent, just finished reading a book about the Scots Irish. He believes that his family was part of this early immigration from Ireland to the U.S., and the people were actually Scots - if I have that right.
Anyway, it seemed kind of neat.
Thanks again for visiting and please come back when anything jewelry related comes to mind!
chris