You can see a Task, Image or Contact on a list if any of the following conditions are true:
- You created it
- It’s on a list you created
- It’s shared with you by another user
If any of those are true and you still don’t see your item, check if you have a Filter set on the List. i.e. click on the 
icon at the top left of the list. You may have set a Filter than only shows e.g. items with a Status of ‘To Do’ or only those with a particular Tag. If that’s the case, you can delete the filter (so all items are shown again) by tapping/clicking the trash can icon on the Filters page.