If you ever find yourself inside the Ahwahnee Hotel in Yosemite, check out the paintings by Swedish/ American painter Gunnar Widforss. They are all over the lobby and some of them are huge. All watercolor and painted about 100 years ago. Some are better than others (just like with any painter) but they are all worth looking at. From what I heard, he was strictly painting outside which is remarkable given the sizes of some of his works. A truly dedicated artist!
Widforss painted the tunnel view (Yosemite) in his time. Nowadays you mostly see photographers there to capture the sunset. I also painted it many times in all kinds of weather/ daylight.
Anything can be good painting material, depending on the condition. Not many watercolorists tackle cascades and waterfalls as they are quite difficult to paint. In the right light, though, it can be a wonderful subject.
Before painting anything I always look for the following aspects:
Will the light work as a painting vs. as a photograph? This is not as simple as it seems. Often I am tricked into believing that a scene/photograph will make a great painting only to find out after painting it that it didn’t really work out the way I thought it would. Experience helps here.
Will the value pattern work? Just making sure I have everything from super light to super dark somewhere in the picture. There is nothing worse than a painting that’s all mid-tone.
Am I emotionally invested? If not, forget it! In other words, if I am not 100% sure I like the scene, if I am not really psyched, I won’t paint it. Done that many times and the resulting painting was always mediocre, at best.
Do I have a strong design and composition? Are there areas that seem unresolved? Is my focal point there?
This is also tough to judge, especially outside. When painting watercolor it is easier because there is drawing time first. While drawing it is often obvious what’s not so great and fairly easy to change before the paint goes on. In oils, I can always scrape off areas but that is definitely best avoided.
Lastly, I will think about my color palette for a particular painting. It is important to have good color harmony and think about the interaction of color in all the major shapes, i.e. foreground, middle ground and background.