People I follow have posted, but nothing's popped up
I'm guess this might be posts imported through importer tool.
Those do not appear in fresh art and likely newsfeed as well, as importer may import hundreds of submissions at once and they would flood the areas.
I wanted to give an update here. We've had some site updates since this ticket was submitted, and if this was an issue, it should be fixed now. I'm going to echo what Rykomi said, though, and that users can upload images without having them go to the main gallery.
Customer support service by UserEcho