Its not really a "supersize" function as its the size of the image you upload. I resize my pictures smaller in PhotoShop to 72 pixels per inch and into a 6 x 8 inch or so aspect ratio. The smaller "thumbnail" shows up in the thread's posting and once clicked on, goes to full size. Hopefully you have an image-editing software where you can do the same or similar to your photos.
Hope this helps.
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