Kinja is designed to be a flexible layout, for optimized viewing on as many devices as possible. To meet this standard, some of your images may be adjusted by the following rules:
Any images 800px or larger will take up the full column width of 800px
Any image smaller than 800px but greater than 400px are centered. These images become full-width as the column gets smaller on smaller screens
Any Image smaller than 400px are floated to the left of the column. These images become centered at the portrait tablet screen size, and become full-width as the column gets smaller on smaller screens
You can see these rules in action on this test post. Images that are shrunk to fit these rules will have an Expand button on them, which will allow you to open the image in a light box to view at its original size. Custom dimensions entered in Kinja's HTML view will be ignored; all images currently adhere to the above rules.
Images in posts that you've authored can be recommended, which will feature the image on your blogs homepage.