How to manually add an artwork to the iTunes Artwork directory? I would like to add an artwork to an album which has files saved in .wav format. I know that it is not possible to attach an artwork to a wave file, so I'm trying to add a standalone artwork.jpg file to the album in iTunes.
I found out that:

it is not possible to attach an artwork to a track or an album directly
placing an artwork.jpg file in the album's directory doesn't work.
I learnt from other sources like this that there iTunes saves artworks somewhere in the Album Artwork folder (probably here: /Users/user/Music/iTunes/Album\ Artwork).

My questions are:

Is it possible to add an artwork manually somewhere in that Album Artwork folder?
Is there any other hacky way to make iTunes actually load an artwork to an album in .wav format?

Note: The album is not available on the iTunes store, so the album hasn't got the official artwork which could be downloaded by iTunes on its own.

Note 2: the traditional way of adding an artwork using Get info does not work for .wav files.

Major update:
It turns out that it is possible to add an artwork to any album in iTunes. The format doesn't matter.
There is one more problem however: it is not possible to add an artwork to an album which has only one track.
Is there a way around it?
Just find the track [or the entire album] in iTunes, select it then hit  Cmd ⌘   i  to get info.
Select the Artwork tab then drag your picture from Finder into there.

Unfortunately, this appears to work for just about any format except WAV.
This also applies to an overall 'album' artwork added to the folder rather than files. It will only work if they are not all WAVs.  

I'd suggest perhaps converting to AIF, which would be a completely lossless conversion.