There should be an empty file called .nomedia in your album artwork folder or above on the phone that tells your phone not to include that directory (or any folders below it) in your photo gallery. Mediamonkey (I'm pretty sure) puts one there. Maybe it got deleted or corrupted somehow.

BTW it's most likely not "copying any files into your photos" Your "photos" are actually the contents of folders that already exist on the phone as scanned by whatever gallery app is on the phone, so you're not losing space and these aren't additional copies. It is, however, annoying to see a bunch of album art when you want to look at your pictures in your photo gallery, which is why .nomedia exists.

There are probably also manual ways within the photo gallery itself to either include or disinclude specific folders on the phone from the gallery.

MediaMonkey: 4.1.17.1840
MediaMonkey: 1.3.0.694
Moto G4 Phone

I have always used mediamonkey for sending individual albums to my phone. Never had a problem like this before.
When I sent albums to phone it would never leave the album art in my photos folders. The Tracks had the album art inbedded.
Here an example:

Wonder Woman Soundtrack has 15 tracks
What I end up with is 15 Album art in my photos folder
or
X-Files Volume 1 has 94 tracks
I end up with 94 album art in photos folder. Thats the same cover art on my sdcard 94 times.

Somehow the album art is transfering to my photo folder and remains connected to tracks in the album. I delete them from the photo folder and the tracks in mediamonkey lose their cover art.
If I delete some of the album art, not all, then some of the tracks in mediamonkey lose their cover art while ofthers do not.

I have tried to move the albums via windows explorer and get only one art cover in the photo folder instead of the art numbering the same amount soundtracks tracks.
I checked through the independent filemanager and the same problem is shown there too. The images are shown and if I delete the art and the same happens.
If I remove the album the normal way through mediamonkey then the album art in the photo folder are also removed.

I have unistalled mediamonkey on my phone and thene reinstaled an up to date version. Still same problem.
I dont want to send to my phone The X-files volume 1,2,3 to my moto g4 and end up with 317 album cover art in my photo album and taking up my space micro sd card.

Need some help here as I am at a loss as to why this is happening. I want to continue using the "send to" facility in mediamonkey to transfer my music to my phone and not have to go through windows explorer everytime.

Thanks for any help given.