Here are some codes. Some may be invalid so don't be surprised.
chimbu - 500 gems
explorer - 100 gems
ngkidsrox - 1000 gems
discovery - 1000 gems
ajbday - 3rd Birthday Cake
bemybuddy - 500 gems
ajhq3000 - 500 gems
10million - 10 Million Banner
ngexplorer - 1000 gems
drawing - 500 gems
hooot - 500 gems
alphas - 500 gems
kangaroo - 500 gems
koala - 500 gems
dolphin - 500 gems
chimbu - 500 gems
explorer - 100 gems
ngkidsrox - 1000 gems
discovery - 1000 gems
ajbday - 3rd Birthday Cake
bemybuddy - 500 gems
ajhq3000 - 500 gems
10million - 10 Million Banner
ngexplorer - 1000 gems
drawing - 500 gems
hooot - 500 gems
alphas - 500 gems
kangaroo - 500 gems
koala - 500 gems
dolphin - 500 gems