I don't have any albums only tracks.
If your songs aren't tagged with album name just artist and track name, this entry in preferences/Internet/custom web links will use your browser to search Discogs with the artist and title from the song, normally displaying the album cover and album name the song is on in the results. Then you can copy/paste or download the image from there.
https://www.discogs.com/search/?type=all&artist=<Artist>&track=<Title>
This works for a track title-plus-artist search from a MusicBee web link on that site:
https://germancharts.de/search.asp?cat=s&artist=<Artist>&artist_search=starts&title=<Title>&title_search=starts
This website's searcher can do a "starts with" or "exact match" search for both or either term. The one above does a "starts with" for both track and artist; to change either or both to "exact match" change the word "starts" to "exact" in the code string.
Once you actually do a search using a website's search GUI, most of the time it's easy to pick up the context for a code string by just looking at the what the URL changes to in your browser window at the results page.
I noticed that you can go directly to the detailed song results that include a small album art picture and album listing with this code:
https://germancharts.de/showitem.asp?interpret=<Artist>&titel=<Title>&cat=s
Happy MusicBee-ing! :)