how the storage work ?

No, the storage limit does not reset. If you reach the limit, you can free up space by deleting submissions, or upgrading to a paid plan that best suits your needs.

Yes, you can upload images, you might like to see these guides:

https://www.jotform.com/help/29-Upload-Field-Allowed-File-Types 

https://www.jotform.com/help/33-Changing-the-Upload-Size-Limit 

Let us know if you need more help, we will be glad to assist you.