The reason you can only load one picture at a time is because the picture file size is huge.
If you have software to modify the picture call it up. Then reduce the image size to something like 1200 pixels wide. When you do this, there should be a box that controls the resolution. It's usually around 200 dots per inch. Reduce this number to 80. Watch the image size when you do this. Some programs will shrink the size as well as the resolution. If the size shrinks down, reset it to 1200.
Making these two changes will reduce the picture file size from 3 megs down to around 80Kb.
This will allow you to post more pictures in one post.