I dont have much interest in this, but for the sake of the whole fantasy setting ... verisimilitude, spit... blargh... what a disgusting word, it would be preferable to have this race be at least a bit more original then just "pretty humans" they were morphed into.
Maybe the bodies could be made slender and not as tall as humans, maybe not. Maybe the facial shapes can be adjusted a bit like already covered here.
But i would like to suggest one relatively very easy to implement addition, that although it may not be supported by the actual official lore material - which btw, stole most of their fantasy races ideas from J.R.R Tolkien and turned them into mass marketing product - would make Elves and their hybrid variants stand out in a very recognizable and unique way.
We already have several types of demonic eyes based around the concept of black sclera and radiant irises.
I suggest elves get their own unique types of eyes which would be full color iris and sclera (the white part) with some kind of a pupil. The sclera and the iris would be of the same color with options of different color variations, darker and lighter blue or green and so on. These kinds of eyes would very visibly present an "alien" and "fey" aspect of another different race. While Tieflings have their demonic eyes, Elves should have the "heavenly variant" as a contrast. The iris and the pupil can also be shaped a little differently to enhance the sense of otherness.
