The File a Support case link is in the right hand column on the Help page.
In your photo editing program if you set the size to 1024 pixels width when you save it after making your color and brightness changes it should be around 1 meg or less.
When you upload your 2 megabyte images we're resizing them and they are likely only about .1 or .2 megs each. So 1 auction of 20 of your photos likely only takes 1-2 megabytes total.