Hello Adriana,
You know, I've been thinking about this one for a few days now. So here goes...
First of all, your artwork is fabulous. It is magical, whimsical, fun, and communicates an intriguing story.
That's why the comment you received at the SCWBI conference is so disturbing. Anyone who offers a critique that leaves you feeling as if you were just (figuratively) "kicked in the stomach" has other issues and, therefore, as others have suggested in this forum already, you should just ignore them.
BUT, we all know that is easier said than done.
That's not to say that critiques from those with your best interests at heart should be ignored. I truly think your work is very good and any flippant comment about it being "too photo-shoppy" is simply not going to help you in any way. In fact it could hurt you, discourage you, and derail your ambitions.
ULTIMATELY, the BEST critic of artwork for a children's book is a child. Read that again: THE BEST CRITIC OF ARTWORK FOR A CHILDREN'S BOOK IS A CHILD!
Ha! I just ticked off every agent, art director, editor, and publisher. But, trust me, if a child is mesmerized by your story and illustrations you have succeeded.
Both Thomas Kincade and Norman Rockwell were heavily criticized in their lifetimes but THEIR AUDIENCES adored their work.
Meanwhile, Andy Warhol is considered an art "god" and he painted soup cans. Go figure. But, still, it is ultimately his audience that matters. My taste doesn't really matter. And THAT is my point.
Your audience is who needs to appreciate your work.
So, take heart, I've seen a lot of children's books and been to a lot of readings of children's books and when a child is engulfed in every word you have written and in every illustration you have painted you have a hit.
Just to backtrack, I'm sure the best agents, publishers, etc. agree with this and make every effort necessary to look at stories and artwork through a child's eyes.
It is asking the impossible to ask artists to grow a "thick skin" to ward off negative or thoughtless comments. If you weren't sensitive, you probably wouldn't be an artist.
So, I hope this helps. If I reach you in only one way with this writing I hope you can rest assured that your artwork is wonderful.
Keep up the great work.
Larry