Photovoice as developed by Wang & Burris was certainly embedded within the context of participatory action research, however since then it has become more widely used throughout qualitative research. (Some people prefer to use the term "photo elicitation" for this broader use, and thus reserve photovoice for more participatory applications.)
Either way, you want to use some version of purposive sampling, where you specify who the eligible participants are.
If you tell us more about your research goals, we can probably give you more advice about an appropriate purposive sampling strategy.