It is something I have been bothered with ever since the game launched and I got my first vampire character. For all non-vampires there is a distinct difference between the elf races and the human races when looking at their eyes. The elf races have large irises with almost no whites in them but when they become vampires (at least for my dunmer, which is the only vampire I have) they suddenly get more human looking eyes with smaller irises.

This change of eyes is very clear in vampire stage 1 and 2:


In stage 3 and 4 the eyes look a lot more like elf eyes, where the whites are black and the iris is white/red:


Compare these with normal red eyes for a dunmer:


Both argonians and khajiits get cat-eyes as vampires so it should not be difficult to give the elf races a unique pair of stage 1 and 2 eyes instead of the human version.