One way to do this is simply to create a new table in your database and call it itemimages or something like that.
have a unique id as PK, an itemid as FK to your items table, and a field for url path for your image.
This way your database can store as many images as you require for each item.
(NB Your item insert page will need to be slightly more complex, storing most data in the items table, and some in the itemimages table, so you will need a normal insert behavior, followed by a multiple insert behavior.)
good luck