What also works is Wikimedia Commons. There's a good mobile app. You can take pictures of a POI, upload them and later associate them with that object in OSM (or via Wikidata).
The wikimedia app could be improved a lot to support OSM. It is a bit of a hassle to take a picture, upload it to commons, then add both categories and concepts, then open an OSM editor, find the object, and add the wikimedia_commons tag.
It would be much more helpful if you could search for an object in OsmAnd/organicmaps etc, take a picture, have it uploaded to wikimedia providing default categories based on OSM tags, and then have it added to OSM. It could also help create wikimedia categories if necessary.
A lot of the images are too dark or low-contrast, so another nice feature would be to auto-adjust the image for brightness (maybe make this a user-level default).