Thanks for all of your great work. The "positive" we're looking for isn't so much about the plus sign as it is positivity and happiness. I think the quality of your work is fantastic and would love to see what you came up with if you substituted positive with happiness in your thinking.
I REALLY like #34 except for the fading different shades of yellow and green (I think that will be difficult to print). Also I wonder if it might be good with some sort of eyes (circles) above... your call.