The licensing you attribute to your uploaded content gives you control over how others have permission to use your photos. You can learn more about the different licensing options here.
Keep in mind, while attributing a stricter license to your photos aims to discourage others from downloading your photos, there will unfortunately always be people out there who may disregard this & attempt to download your photos anyways.
The only way to entirely prevent this possibility is to remove your photos from public view & make your content private.
Below are some other ways to better control who is able to download your content:
- Limit access to your "original image."
- Limit the size of the image you want others to have access to.
Creative Commons license