Most everyone now has a cell phone that includes a built in camera. Now a days there is no excuse for not taking loads of reference material.
I see so many students using photos from the internet, newspapers and magazines and those may be okay in the beginning to learn to paint from, but as you get experience under your belt, it will be time to gather your own reference materials.
Choose
subject matter you love and know a lot about. Those two choices are the most important when it comes to choosing subject matter.
If you love and know the subject matter you are painting, it shows in the painting when you are creating.
This photo was taken while walking through the botanical garden in St Louis last week. It took about 3 seconds to take. I took about 4 shots of this same plant from different angles and this one was the best shot, the
rest I threw out. Since it no longer costs to develop film, when you shoot for reference, take loads of the same shot from different angles, then pick the best to paint from.