In the past, improper image resizing used to be a big no-no of web design (not mentioning improper compression format). Hence, for years I have been sticking to the policy where images (PNG or JPG) are resized on the server to match the resolution pixel-wise they will have with the rendered page.
Now, recently, I hastily designed a HTML draft with oversized images, using inline CSS style such as
height:123px to resize the images. To my (slight) surprise, the page turned out to look much better that way.
Indeed, with better screen resolution, some people (like me), tend to browse with some level of zoom (aka 125% or even 150% zoom), otherwise fonts are just too small on-screen. Then, if the image is strictly sized, the enlarged image appears blurry (pixel interpolation effect), but if the image is oversized the results is much better.
Obviously, oversizing images is not an acceptable pattern if your website is intended for mobile browsing, but is there case where it would be considered as acceptable? Especially if the extra page weight is small anyway.