Publishing a result that is aesthetically pleasing, but has no practical value I am currently writing a paper that I wish to publish in a mathematics journal. During the course of my research, I have discovered a result that is aesthetically pleasing, i.e., contains a form of symmetry in its definition that can be seen by some as "elegant", and moreover connects several distant theorems together. However, this result turns out to be useless for practical use, furthermore it adds nothing to the other proofs and theorems presented in the paper. Is it worth publishing/mentioning, even as a corollary?
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.