But somehow I'm glad that I finally found out I'm not the only one with this problem, hahaha. Spotify has to fix this asap, it's so annoying.... The pic I chose (the right way round!) is is shown in the frame 90 degrees rotated and now it's not possible to undo it.
I tried to change it on by brothers notebook, I reinstalled Spotify, I logged out and in...
I don't want to create an new account bc of this!
To everyone else who's annoyed bc of this- I feel you!