I have an 11 year old Iris and dd2 was nearly a Violet. We don't know any other Iris' and only 1 Violet, so neither are super popular at the moment.
Both are elegant and grown up. I agree with Squoosh that Lily and Ruby are cutsie, and seem to have a broader appeal.
Mumsnet is not representative of the world at large I don't think! So whilst Mumsnet says Lily (or whatever) is too popular, and over done, most people don't agree and call their kids Lily (or whatever) anyway. I don't think anything outside the top 100 can be seen as too popular.