The best thing to do is first create a new Picture Library and upload your images into this. The default folders that come with a new place can be problematic.
The Page folder
In the Image Manager, if you upload images into this folder then an error will appear when you try to publish the page. This error will stay with the page even if you upload the image into a new folder and try and publish from there. The only way to remove the error is to click out of the page and then go back to it.
The Publishing Images folder
Any images uploaded and published via this folder will only be visible by the user that uploaded them.