Adding a photo to a signature box and resizing it so it's not huge

I am trying to create a signature block with my name, address phone, etc and add a photo below the text area. I can drag a photo into the signature set up area but then it appears huge in the actual email that I want to send with the signature line attached. Is there a way to size it appropriately - add a frame maybe that the photo can sit in. iPhoto doesn't seem to let me resize and image - either pixels or canvas size. Any ideas are appreciated. Thanks