Working great, placing high quality pictures of the artist in the "artist picture" frame element! Using MusicBee 3.6.9198 P, Windows 11 x64.
Question: can you tell if the picture is from last.fm or wikipedia within the MB interface?
Comment: the plugin is downloading the original picture as found in its original size--which is the desired action. In cases where the frame provided cannot display the original size, the picture is cropped to its center and resized to fit the frame, aspect ratio maintained. Double-clicking within the "artist picture" frame brings it out of the MB GUI in its full size. Sometimes the original can be quite large, like 1920 X 1080. Would it be better to resize first to fit the frame, using original aspect ratio, so that the entire image is being displayed there? The current crop to center action can be kept as an option.
Plugin as default with original image auto-cropped to center to fit display frame:

Double-click opens full downloaded image size (1920 X 1080, reduced here for Forum post)

These pictures are stored as *.dat files in the ...\AppData\InternalCache\ArtistBackdrops folder. The cache is not cleared automatically.
Thanks again for this vast improvement on the original Artist Picture element!