To be honest, the people against that kind of promo could be only the ATK guys, since their photos are the main content of this site and you should be feeling happy cause he's upselling your site on a free site with ATK content.
In this particular case I don't see a problem, cause he's just using your pics for a banner which is linking directly to your site.
I'd be worried only if your fullsized pics were on a gallery with ATK banners or the opposite - ATK content/FurryGirl banners. Thus, that's not the case and you really shouldn't feel weird about it
FULLSTOP! Gotta get back to work!