The new Google Profiles border lets you upload multiple profile photos and button between them with a simple click. Visitors can see all the photos you've uploaded, so you must be cautious when you replace a profile photo. It's not enough to click "change photo" and upload the latest image: you should also click on the image and delete the preceding profile photo.
Profile photos are stored in a Picasa Web album, just like the photos from the Scrapbook section. The main dissimilarity is that profile photos can be cropped or shortened in Picnik.
If you previously have a Google Profile, it's a superior idea to upload a new profile photo. The new border uses bigger photos, so your old avatar looks pixelated.