The Peyto Lake overlook may be the most dramatic viewpoint on the Icefields Parkway. This photo was taken in the late afternoon when Peyto Lake is in shadow. The best time to take an evenly lit picture of the lake and the Mistaya River Valley to the north is the early part of the day. You'll encounter smaller crowds at that time, too. If you visit during the summer months you'll see a nice display of wildflowers along the trail from the lower parking lot to the viewpoint.
The Parks Canada website has a photo which shows most of the lake and part of the view down the Mistaya River Valley. Peyto Lake is location 4 on this Parcs Canada map of Banff National Park.
Here is a nice panorama of Peyto Lake by Juan Abal that is posted on www.webshots.com. In this photo you can see the beautiful blue-green color that glacial till imparts to alpine lakes.
Ash Creek Images
Photographs of the West by Doug Gorsline
A Vignette of Peyto Lake Photographed from the Parks Canada Viewpoint, Banff.