It took me a few days of playing at the Picnik website before I noticed this goodie in my picnic basket!
The collage tab is on the home page. (Don't ask me how I didn't notice it for days!)
The good folks at Picnik have a great tutorial to walk you through the steps. You can see on the bottom of the screen are your photos, you can easily add more. To create the collage it is as simple as picking your template and dragging the photos to add them to the boxes.
After you create you collage, you'll notice some adjustments you can make - one of them being my beloved round corners. You can also change the background color here too.
Okay, now just so we are clear - I'm not responsible for time wasted playing with this new toy!
Use this feature for easy tutorials like the one I did on the Art Bead Scene. Jazz up your blog posts or newsletters. The collages can even be used in your printed material. Save them on the high quality setting.