that's super nice of you to put the thm file in there..
you also need to put the cod file have to have both.
as for pics, you can do one of two things
1) put pics on an image account like photobucket and then use the image url by clicking the little yellow square with a mountain/sun in it and cut/pasting url into the script window.
2) use the 'go advanced' button at the bottom of the quick reply box and then at the bottom of the screen click manage attachments.