Go to your Tree Settings > Privacy Settings > make sure you either have "Public Tree" selected or, if you have Private Tree selected, be sure that "Also prevent your tree from being found in searches" is UNticked. Everything in your tree should then come up in search results, though if it's a private tree, access will be restricted.
I believe the exception to this is if you've attached the photo to a living person. For privacy reasons, photos of living people will obviously be restricted. Make sure deceased individuals aren't incorrectly set as still living.
If this doesn't help, you may have better luck posting this in one of the boards regarding the Ancestry.com website/member trees - this is more a board for discussing photography, not the functionality of the website.