There is no doubt that Celtic--and certainly Irish--art was influenced by
many sources, but it is difficult to identify many of them. As Francine
noted, the folks of early Europe were much more mobile than we generally
assume. At the same time, imagery is accepted as developing independently
in different cultures. Art historians don't assume that because similar
images occur in various cultures there is a direct connection, although
this is very seductive. One must follow the imagery backwards very
carefully during the research process. It is often the case that there is
no connection whatsoever. I have read nothing that would definitively
connect your Islamic designs with Celtic or Irish ones, but neither is it
beyond the realm of possibility. Nor do I have knowlege of any scholars
working in this area to whom I can direct you. Sorry.
My research areas are bronze age European and medieval Irish art. I have
two colleagues in Asian Art . One studies south Asian art (Pakistan &
India), the other east Asian (China & Japan). In the past, as I organized
my slides for lecture, both have observed similarities between the arts of
their subject areas and the Celtic and Irish imagery they have observed in
my slides--particularly the manuscripts. We have never followed up on this,
but threaten to regularly.
As for the Irish interlace motif(s), it's pretty much accepted that they
are considered to be protective as well as ornamental. I'm sorry that I
don't have the reference here, but several years ago a very good paper was
published that made an excellent case for this. It dealt specifically with
illuminated manuscripts, I believe. Within a Christian context such as
manuscripts, we don't say that they were intended to 'make magic,' but in a
way they were believed to do so. Certainly, interlace is seen as possessing
certain protective powers, as I've already mentioned. It is also believed
that the process of creating and looking at the intricate designs found in
Irish illuminated manuscripts was meditative and allowed the scribe--and
afterwards, the reader--to achieve a heightened sense of the
Birds of prey, swans, geese, and ducks, as well as serpents and dragons,
are also interpreted as possessing protective qualities, btw. They are
often found on the accoutrements of warriors.
I don't know if any of that helps you at all, but perhaps it's relevant.
Oh, and yes, I have a degree or three--in art history, even.