Embellishments: Stickers, borders & text can add a personal touch to photos. I used a photo of my beautiful and beloved cat Sammy, who I sorely miss every day. I'm going to move onto the next photo now for fear that I'll start crying.
Effects: These are to make your photos look uber cool. There are heaps of really cool effects to chose from and it took me a long time to settle on what ones to do for the demonstration. I used fairly simple effects on this photo of the girl running with the balloons, but I think they still look pretty good. To me the above photo kind of looks like daytime and dusk. Except the sky's slightly orange and her balloons have changed colour. Oh well! I used HSL Filter in Sandbox Effects for that effect. The bottom one shows an effect that I use all the time. I just made it black & white, and then used a paint brush to make the balloons their original colour. Simple but effective. Funny that.
Touch-up: Last but not least, this demonstrates the main purpose of Picnik; to make your photos look nicer. For this photo that I took at the Hamilton Gardens (which is the best place in Hamilton for great photo opportunities, in my opinion), I tweaked the colours so they looked brighter and fuller, and also sharpened it. If you enlarge the picture you might be able to see that in the right version of the picture you can see a bit of dewy-looking stuff on the flower. I think it might be rain, because it had been misting over a bit when I was there.