This is just a beautiful name. I also love Lily and Lillian (not Liliana) but Lilias is so unique. I've never even heard the name except in 'The Secret Garden' and names I have given to characters. I would definitely use this for my daughter, if I ever have one, maybe combined with something else flowery and beautiful. Lilias Poppy, for instance, or Lilias Daisy. This name deserves to see more little Liliases running around.
I love Lilias. It has such a lilting sound to it, is youthful and soothing, and very gentle. I do like Lily, Lillian, etc. But Lilias is better and more unique, and I like it's Scottish, as well as that Lilias Craven had this name. When I hear this name I think only about nice things - Scotland, "The Secret Garden", lilies, and flowers in general, nature, smoothness and softness, long, green, juicy grass, leaves on trees moved gently by the cool wind, a stream lapping, lots of greenness around, I see this name in green, or kinda feel it's green, I also think about violin and harp music when I think of it. When I try to imagine a Lilias, I see a young, innocent lass, who obviously loves to be out in the nature, is musical, gentle, sooo very girly, but not overly frilly or anything like this, just has a lot of youthful charm, and is a little otherworldly so to say, definitely a dreamer and romantic in a way, is rather calm but likes to laugh and is very bright, kind-hearted and enjoys every little moment of her life. It all sounds pretty poetic, but that's how I find the name Lilias - very poetic and gentle - and I think all these associations are very cool.
This is such a rare and unusual name; I'd say it's unique in English-speaking countries, having a feminine name ending in -s. I mean usually it's masculine names such as Rufus or Regulus that end in -s, but I don't know, it sort of goes quite well, I think. :-)
I do not enjoy the name Lily much, but I really like this name (recent discovery!) Love the 's' at the end! Kind of, I dunno, wraps up the name, doesn't keep the sound hanging like in the end of Lily. Plus I just like cool endings. Didn't even notice it was used in The Secret Garden, totally liking it even more now. =)