Well, if it's your stash, what a lovely way to go!
When you hit the edit button on your post, what you have submitted will show up (you won't see the pics though, only the browse/description box).
By each picture, there is an option to remove. Just click remove and it will take that one off. Then you can submit another in its place. :)
I've seen others who've posted connections to their blogs and other personal sites. I've never done that, but I guess it's like posting a URL...just go to that site, right click the URL, go to edit and copy, then come back to your posting and paste. MoonPi and some of the others are way more computer savvy than I am. I'm also a little computer paranoid.
Good luck!