I don't understand the question. Where/how - does MC have any say over art quality?
If you copy & paste art, Media Center resaves it as a medium quality JPG.
Media Center will also
only add JPG art to files, so if you have lossless PNG art for something, it will be resaved at a lower quality when MC embeds it in a file.
Sure, it's only a handful of albums which have PNG art, but why would you ever want to replace a lossless file with a lossy version? (even 100% quality JPG can show compression artifacts)
Every art file is a jpg, lovingly prepped in Photoshop at 500x500 pixels and all my cover art looks outstanding.
You might want to reconsider 500x500. With modern phones coming with 1920x1080 screens, and tablets with 2560x1600 and beyond, that low resolution art doesn't look so good any more. Televisions will be moving to 4K soon, which is even higher resolution.
The highest resolution art I have is 3400x3400, though most are around 1500x1500.
If quality is being effected - AFTER I add my art - that is an issue - or am I misunderstanding something?
The issue shown in this topic, is when displaying art in the library view. As you resize the thumbnails, MC snaps between different quality levels, so if you are below a certain size, it's full of JPG artifacts as shown above. The "high quality" images are how the art would look without that compression. (I resized the source files in Photoshop)
iTunes has no problem adding PNG art files, and I don't seem to recall it using compression for its thumbnails either. (it has been a while since I used iTunes though)
And when resizing covers that have fine text, as with the two
Carmen Gomes Inc. albums, it's also best to be using linear light scaling. (in Photoshop, this means doing the resizing step in 32-bit)
It would be nice if Media Center could do the same.