I am sorry you really want to cancel the account you have invested so much of your time in. I do agree that the cover image takes up much space when the page is launched on the mobile phone, but that is not the case with desktop, or laptop. In any case, I see it as an advantage.
1. It personalizes your page, and helps customer who favors your photos to easily identify you. That do serve as an advantage for increased sales for you. I once changed mine, and it did affect my sales, I had to reverse the change.
2. If you have your best photo there, it serves as a means to attract new customers to your page - customers that will bookmark your page and return every time they need new images. I believe having the large view on the mobile phone is a good thing, since it helps customers to have a clear view of that image. That can help to spark multiple sales for that image. Besides, the image do scroll with the page, so it is not a case where it is obstructing views of the others.
Bust if those advantage for increased personal sales is not good enough reasons to want to keep one of your images as a cover page, you will need to follow the directive at https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/submission-guideli...
to close the account.
No-can-do. Only you can delete images and only you can delete your account. Fellow users cannot help you with that.
To cancel your contributor account you must send a request through the contact us form found at the bottom of the Adobe Stock Contributor Portal. NOTE: If you delete the account, you won't be allowed to contribute to Adobe Stock. Is that really what you want?
You can delete your account, but if you want to create a new account you will have to go through the whole process again and upload ALL your images again.
Also, in the new account, a banner will still appear as that is part of the layout. So, there is no point. At this stage, there doesn't seem to be a layout for the mobile version. On the smartphone, you get the desktop version.