I remember on the Galaxy S3, the contact icons were rendered very nicely, but on the S4, they're not rendered that well, no matter how high-resolution the picture size.
The screen size is 1920x1080, and I've measured the actual contact icon as 163x163. The screen's resolution is 441ppi.
I've tried creating my contact photos at 1080x1080 at 150ppi, 200ppi, 441ppi...you name it. The picture looks fine in original size and on the Contact's profile screen, but on the actual Contacts screen, the icon looks extremely jaggy. The best I can do (my current setting for my Contact photos) is 163x163 at 200ppi. That's when they look their best, although still not very well rendered.
Is there anything that can be tweaked, namely in the Developer Options, to render the icons better? I know it's no big deal, but that's just something I wonder. (Again, this was better on the S3.)