I don't know anything about MusicMatch, so I'm not familiar with what you had. WAV files don't store tagging information inherently, so if MM was something that ties files to metadata (tag info) in a repository that is now no longer available, you're probably out of luck.
Assuming you have your WAV files on a local hard drive under your control, I'd do the following:
1. Convert the WAV files to lossless WMA, or other lossless format that supports tag info.
2. Get a new music "jukebox" for the computer - iTunes, Windows Media Player, or other. My choice is J River MediaCenter, but there are many.
3. Import your converted files into the music jukebox.
4. The jukebox should have functionality to go out and lookup metadata, including cover art, from the internet, as well as to enter it manually as desired.
Then you'd have it all under your own control.
Assuming you have your WAV files on a local hard drive under your control, I'd do the following:
1. Convert the WAV files to lossless WMA, or other lossless format that supports tag info.
2. Get a new music "jukebox" for the computer - iTunes, Windows Media Player, or other. My choice is J River MediaCenter, but there are many.
3. Import your converted files into the music jukebox.
4. The jukebox should have functionality to go out and lookup metadata, including cover art, from the internet, as well as to enter it manually as desired.
Then you'd have it all under your own control.