A trigger object will work if the things you want revealed are spaced apart vertically. But this is not a really good solution.

The problem with layers I think is they are fixed, so if you are calling up a layer then content on the layer will need to be the same place as on the screen.

Can you provide a visual of what you are trying to accomplish? To upload a file or image, click the Go Advanced button under this window, scroll down to Manage Attachments, then browse to and select the file or image you want to upload.