Here are the steps for getting images into StoreIt. First thing to note is that the pictures need to be in your iPhone or iPod Touch Photo Library.
Here's good tutorial on the web for getting photo's into iTunes and then onto the iPhone.
http://artoftheiphone.com/2009/01/04/how-to-add-photos-to-itunes-for-synching-to-iphone-or-ipod/
Don't miss the handy hint in the final paragraph at the end under other notes which describes how to get individual photos onto the iPhone without going through a sync. (This also works under safari, if there is an image on a web page that you want to capture put your finger on the photo for a few seconds and you'll get the option to save the image to your library.)
Now you can get the images into StoreIt.
1. Add the image field to your category.
2. Open up the item you want to put the image on and press edit.
3. Press the Add image box.
4. Your Photo album should now be displayed which you can browse and select the image you want. Select that image.
5. Save the record.