what you need is called Anti-Aliasing. It has nothing to do with the formats. I don't know how those images were rotated, but they weren't done in photoshop were they....
Why you use them if all images have same link : psdworkshop.com I know..this template is a movie related template and there was images with link to movies (posts) but you can change the header to display a single big image like this but retouched in photoshop. Or use a flash carousel witch is better than this javascript.