Scratch

Hello, this is my first post. Anyways I've got a project: this one, click here, and as you can see, it's an interactive Wii cursor that follows your mouse. I stopped the project in Scratch and the thumbnail of this project is the cursor at the corner of the stage, because the cursor followed my mouse up to the stop button. Well, I wanted the cursor to be in the middle so after I uploaded the project I just put in a when space key pressed, stop all script, then I put the cursor in the middle and pressed space. So that was my new thumbnail--the cursor in the middle. Now here's the problem: I reuploaded the project, and it kept the comments and everything, but it did not replace the thumbnail with the one I wanted. So...how do I replace it without deleting the whole page and uploading a new one?