Publishing a result that is aesthetically pleasing, but has no practical value
Yes, this is fine.  Math papers very often contain results just because they are interesting or instructive, even if they do not seem to be "useful".

You could mention this when introducing the result, with something like "The following theorem may help to illustrate the connection between blah blah blah..."  

Authors also sometimes signal this sort of thing by describing a result as "pleasant", "amusing", etc, though "elegant" is probably a little too egotistical.

If the referee feels it's too much of a digression, they might suggest you take it out.  But I don't think this would be the difference between acceptance and rejection.