Hi,
If you are posting pictures, try and make them a good size to fit in a browser window. Use photoshop/illustrator/any other photo editing suite, to make the pic a decent size (say 600 by 400 pixels). You can also resample the image to make the file size <100kb so it loads quickly.
Apart from that, and like phillip said: click additional options and browse to the picture on your local disk.
Otherwise, you can use i or the likes to host it on different site and post a thumbnail on the forum.
Hope this helps
Graeme Thurston
Access Cleaning Solutions