I increased the size of my Yellowstone Image Photo...how do I repost it? so that it can replace the smaller one?

From the FAQs:

How do I update an image that I've uploaded?
You can update the title and description of an image, but you cannot re-upload an image to take the place of an older image. This is because it could be confusing as to which version of the image people are referring to in the comments and because the old votes wouldn't necessarily be the same for the new image. If you want to change an image or update it, please just upload it as a new image and (optionally) delete the old one.