The first step in learning to paint small figures is to build up a collection of suitable reference photos. You're after photos in which you can see the figures from head to toe, not large photos in which you can see every detail in a figure. You'll be using the photos for shapes, not detail.
There are plenty of public locations where you can take photos of groups of people who are walking, talking, standing, sitting, etc. such as a park, on a street, at a sports event. If you're worried you're going to be stopped by a guard and told you can't take photos, study these summaries of photographers' rights (and consider printing it out to take along with you): USA, UK, Australia.
Don't overlook the potential from family and friends gatherings. Instead of taking close-up portrait photos, stand at a distance and take overall shots. Don't worry if the photos are blurred because people are moving. You're after shapes, not detail.
Another alternative is to hunt through old magazines and newspapers for photos of full-length figures in different poses. Cut them out and stick them into a sketchbook, ready for the next step in the process of learning how to paint small figures.
