There's no serious evidence of anything really, hence why we're all speculating it on looks, possibilities of where it's name comes from, etc.
At least it looking 'airy/windy' or maybe coming from sylph, and the wieght is a way we can see it as a Flying-type, along with a few other possible reasons for that and Normal or Ghost; If anything, Dragon is the craziest thought because that thing doesn't have any Dragon-like qualities(nor does it seem to have anything behind it on that), the colors don't mean much at this point, and they can easily pull away from the whole 'special type' "pattern" if they wanted to.
EDIT: Wow I'm late getting back into this. This response was for an earlier post by metalhand. XD
You know what? What someone else brought up on another site can also be interpreted from the egg-like appearance around Sylveon to help out the Flying theory. The top left part behind Sylveon(while we cannot make it out 100%) looks to resemble a slanted Zephyr Badge(Falkner), the middle section resembles an upside down Feather Badge(Winona), and the last one can just be slightly based off of the Jet Badge(Skyla), so as to not be so obvious, or it could just be a wing...or just Sylveon's ear as someone else pointed out. Although it's all still meaningless as of now, along with the egg thing, that's how it can be interpreted into the Flying theory, haha.