Definitely DEFINITELY - praise your kids for everything. Not, of course, just appearance, but all the other things - kindness, thoughtfulness, working hard at school ...
Alas, my parents were of the opinion that when you had kids, your duty as parents was to belittle, criticise and never, ever praise. If I (rarely) got, say, a mark of 89 per cent in a school math test, my father, instead of saying 'fantastic' (knowing that I had always struggled with maths) would rant: 'How did you lose eleven marks?' Same with being quite good at English - if I had an essay praised, by parents would say stuff like 'Well, the rest must have been pretty awful if your English teacher liked yours.'
I honestly felt their whole philosophy when it came to child-raising was 'we must DESTROY any burgeoning self-confidence we spot in the children.'
I'm in my seventies now and I still bloody SEETHE when I think about this.
Sorry, OP, just gone off an a tangent/rant ... please PLEASE praise your dear daughters and sons, all Mumsnetters [got a bit emotional now 