Just as you can't vote for you own images. You shouldn't be able to set the main profile image to one that you have uploaded.
Added on Jan 11 4:20
I can see why you make this suggestion, but I also agree with Gauntlet. Even if the first picture gets to be the main image by default, there is no way that low quality photos can be identitfied. And especially with lesser known items it can take a while if you have to wait for others to discover that you have uploaded a better image and change it...
Maybe the solution would be to disable you from setting your own picture as profile image if there are already 10/15/20 (idk what's best) pictures of that item from the same category. Or if you are only allowed to change your own picture to primary image if you have a certain listal rank (similar to the ability of changing the item's title). Or if the profile image was based on the amount of votes that it has (see suggestion 590).
What do you think?
Well, I think the population of members who search out a decent image for a person to set as the primary image is relatively low. There will always be the newbie posting custom art or whatever dreadful thing they can find to scan. I have spent many hours hunting down an image for a person that isn't poor quality. So, this idea cuts both ways and would come back to haunt me, I'm sure.
I think that trying to set it based on ratings or number of votes wouldn't really work but you could have a 'sub-admin' type of flag to bestow on some members so that they could override the 'my own image' setting.
Meh, I see this as being a long range problem/debate and for the most part just stick with sites where the primary image is set by admins. I would like to see Listal come up with a solution *any* solution so that the primary image for people are actually a decent quality and not an embarrassment when I have wanted to share this site.