4
This can be most easily accomplished with CSS.
Look at your news_index.html or news_item.html template depending on where the image are being displayed from.
Identify which CSS class or id is being used. And edit the CSS attributes to achieve the results you want.
If this is more than you are up for you could just try another theme.
If you find a theme that displays the image to your liking. Cut and paste the attributes from that CSS into the one you are working with.
Hope this helps,