just figured that out for my self. Got to the url where the pic is uploaded... right click on the image and go to properties. Copy the "address" of the image and paste it into your message (then preview to make sure it works)
Like this but without the spaces... http://www.pbase . com image number / size, medium or large.jpg
if you omit the " .jpg " it will only provide a link to the photo. As was said, preview before posting to be sure it is correct. (I previewed once and instead of a flower, up came a kangaroo! I had entered the wrong photo number!) lol what a surprise! I usually just type the info in myself rather than using the copy and paste method...I just make note of the photo's number.