Use a grid pattern for arrangement and use identical frames and mats. This lends a cohesion to a group of pieces that may otherwise seem disparate, and is a great strategy for displaying your child's artwork. You can find inexpensive coordinating frames at stores like Michael's and IKEA.
A dash of Hermes orange is always appropriate. This room is killing it, just like Jennifer Garner did in the orange vintage Valentino Zoe put her in for the 2004 Oscars.