I understand (or think I do, and have so far) understood the difference between a header and a logo.
However, in the case of
http://k12photoed.org, the only way I found to get the theme to make the header image visible online was to take it out of the wp-content > ata-images > header folder and put it in the wp-content > ata-images folder. So long as I had it in the wp-content > ata-images > header folder, it wouldn't display.
True also at
http://teachingphoto.com
I understand that ATA may be reading my header as a logo in those cases. So long as it displays, I really don't care. I do know that if I move these two headers back into their respective wp-content > ata-images > header folders, they don't display.
In my several other ATA-themed blogs, the header image resides in the wp-content > ata-images > header folder, and displays properly. This is true at:
http://www.nearbycafe.com/loveandlust/eroticbynature/
http://www.nearbycafe.com/artandphoto/photocritic/
and
http://www.nearbycafe.com/artandphoto/liuxiaphotos/
I have no idea why this should be so. But it is. So far as I know, the settings for all these blogs are the same (aside from image location, etc.): headers in the the wp-content > ata-images > header folder, with settings to match.
I consider my primary concern the proper display of the headers at my sites. So long as they survive the ATA updates in their current location and settings (I just upgraded to 3.7.15), I don't really care whether I'm somehow fooling the theme into treating them as logos instead of headers with these two installations of WP/ATA.
I'll gladly send you logins/pws if you want to look under the hood at any of these sites.