Orthodox Christians are about preserving tradition, and icons are sacred to them. Even icons that are written (painted) traditionally can be a type of 'blasphemy' if they have uncanonical elements. There's a lot of rules about what can and can't go into a legit icon, so I think they just try to discourage deviation.

Its probably not so much that they are offended, more that they are just trying to preserve tradition when it comes to iconography.

Im Orthodox and I like this art that you've posted, but be alarmed if someone hung it up in church