When you add a picture in a comment/post, a little file thumbnail is shown at the bottom of the text box, correct? Click the x button on the file, then click the file again, which inserts the picture URL onto the text box. Sandwich the URL with the spoiler codes :) I hope this makes sense.
Dude. That's my artwork you're using for that profile pic. In fact, that was my very first forums profile pic I drew a long while ago. But you removed my signature and then just used it without asking. Not nice.