Wow, I just checked it out. I never even noticed it.
If you don't want any profile pic, just remove it from the page in admin/builders/page blocks/profile or better yet, only upload one image to the profile photo album.
Problem solved. BUT
Why would you want to? I think it's kind of cool and some of your members may wish to use it.
Ahaa, I think you might have just answered my query actually.
So the default photo album every member has, labelled "username's photos" is the album where you inly upload photos of you which you want to appear within the alternating profile picture on your profile.
Any photo's you don't want to appear in your alternating profile photo slot, you need to upload to another album you create.
If this is correct, I think I may change the default name of the album for members so it is more clearer and add this explanation to our FAQ section.
Thanks :)