Something wrong with jrPlaylist 1.1.0
Installation and Configuration
That standalone playlist would be used to embed the player into somewhere. It would take on the dimensions of the location its embedded to.
Docs: "How to embed the playlist player in an external site"
https://www.jamroom.net/the-jamroom-network/documentation/howto/1556/howto-embed-the-playlist-player-in-an-external-site
The image size would be coming from that items modules item_list.tpl file by default. so if its an audio file then /modules/jrAudio/templates/item_list.tpl unless its been over ridden somewhere.