Old capybara evokes a laid-back, relaxed mood, and the light/soft colors matches the easy-going tone of the song. Therefore, the bg is related to/compliments song.
Image is by BS Thurner Hof at https://commons.wikimedia.org/wiki/File:Wasserschwein.jpg and licensed under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license.
