Hi,
I suppose that you are working with the Comnunity Cloud Platform. In this case as reported in the FAQ section of this page http://www.webratio.com/portal/content/en/pricing, you can generate and test your application in the Cloud while you are modeling (although your application will remain in the Cloud for no more than two hours).
If you choose "file" as Storage type the path of the uploaded images is stored on database but after the 2 hours the files are automatically deleted.
To solve it you have to set "database" as Storage Type. In this way the files will be stored into the database.