In addition to taking Country_Wife's good advice, you also might want to take a look at the TripAdvisor page entitled Inside Banff National Park : Scenic Views:
The views that are listed are not confined to Banff National Park. The list includes scenic lookout points in Jasper, Yoho and Kootenay National Parks (which are contiguous with Banff National Park) and in Kananaskis Country, which is to the southeast of Banff.
I agree with Country_Wife that early morning is an excellent time for photography. Another thing about early mornings and evenings is that that those are the times when lake water is most likely to be still. You sometimes get reflections that are so perfect that you don't know which end of your photo is the right way up.
There are a couple of places that I can think of that lend themselves to being photographed later in the day.
One is the view of Spirit Island (which you access by taking a cruise across Maligne Lake in Jasper National Park). Because you face eastwards, it's better to have the sun behind you in the west. I don't know whether or not you've decided to include Jasper in your itinerary, so I don't know if this is relevant to you.
The other spot, which is relevant to you, is when you're positioned just west of Banff townsite and look eastwards towards Mount Rundle. The rock of which that mountain is composed glows beautifully in the setting sun.