I'm using version 2.76, and when I try to save any image, either through right-clicking the image, or using a custom script that uses SCDownload, it always converts it to jpeg.

Is there a way to download the original file and not have it convert the format?

Make sure you are not specifying a width and height when you call your download function. Setting and width and height will download the preview of that size that supercontainer renders for you. Leaving the width and height out of your function call will download the original file for you.

If you specify a width and height in your URL you will be seeing a .jpg which is resized to the width and height you specify. I recommend not using an URL parameters, such as width, height, or the noapplet style. This will let you use the java applet, which will automatically resize your images for you. You can then right-click on the image to download the original file.

Also, please make sure you're using a current version of SuperContainer, there was a bug in an older version that matches some of the behavior you're describing.

http://360works.com/supercontainer/