when I try and upload my banner to the gallery homepage it disappears when I hit apply. I've tried loading it both with the wysiwyg and the html windows

What do you mean with "html windows"? How did you upload at all? What theme?

I have the strong suspicion that you mistake Zenphoto for a website tool box a bit maybe.

I am using the Garland theme. It's in Zenphoto on the Gallery description box. I write the description, which works fine and then when I go to the picture, fill in the url where it is and then hit apply, the image goes away.

You probably have the img element disabled in the allowed tags option. Options > General.

That did it, thanks!