SoundCloud no longer adds Track Banners.
From Soundcloud: Beginning July 15, 2016, SoundCloud will retire the visual track feature which displays a full screen visual behind the waveform.
The visual track feature will remain in tact for those tracks with existing visuals in place as of July 15th, as well as any content which has been branded through ad support.
Why is SoundCloud doing this? While we know many of you are fans of this feature, we do not see it impacting fan engagement for you, therefore we are shifting our resources from the maintenance of this feature, to the creation of better tools and features that will help you drive fan engagement on SoundCloud.