Currently the only way to insert is to use good html links, for which there icon for. I am thinking what might help grow this site if there is a way to maybe have a popup the shows your gallery from an online site. You click the thumbnail and it gets inserted into the post. There might be even an extra box to crop it and scale it if you want to get fancy.
Which site, I don't know. This seems like the community might know which sites allow for something like this and which people usually use. Flickr, smugmug, or something like that would be candidates I have heard of but I am not sure if they allow for this.
This isn't to spawn lots of "How do I make my image better" , but rather to give more context to questions like "There is clipping in high key areas, how might I repair an image that has this issue, for example..."
If someone get something like this going in in greasemonkey we should be able to get it ported to the actual site.