Im trying to make an image show up after somebody clicks "submit" to upload a large video file. Once the button is pressed, I want it to make a gif image appear that will let the user know that its actually doing something, instead of just hanging there. Its all just for show, but I think it will be pretty useful.
I would make the button a normal button. Remove it as type='submit'. Add the java-script to handle the onClick action. Then perform a function call. Once in the function you can acutally submit the form and load the image into a div tag on the stage. Not sure how much detail you want?