I'd say it has enough historical significance to still be acceptable. Consider this: every image compression format out there has an example of their work done on the Lena image. The source code for various compression algorithms may have been lost, but the encoded Lena results for that compression algorithm may very well still exist. This means we can compare between compression algorithms of the past quite easily. We dont have to dig up old source code and find hardware that will run it to compare output - we can simply provide the same input that they had.
Regarding the image itself, it's not even a good test image. There are far better images out there that test the robustness of image compression, but those test images haven't been ran though every image processing algorithm since the 1973. Should we change default test images? Yes, but Lena should still be used as well. The historical data it provides is invaluable.
> I'd say it has enough historical significance to still be acceptable.
This sounds a lot like Redskins argument.
> The source code for various compression algorithms may have been lost, but the encoded Lena results for that compression algorithm may very well still exist.
We need to compare a new algorithm to an obsolete one where we don't even have the source code and this is beneficial... how?
Regarding the image itself, it's not even a good test image. There are far better images out there that test the robustness of image compression, but those test images haven't been ran though every image processing algorithm since the 1973. Should we change default test images? Yes, but Lena should still be used as well. The historical data it provides is invaluable.