I would draw the line when watermarks, logos on a photo or urls in a sigature are posted here only to advertise, and if the website is not related to nature, conservation etc. As long as the photo is in a travel tale or on the ID topic it serves the purpose of our forum.
And we have several members here who have a link to their websites or blogs and perhaps one can buy photos there, too
My two cents only, do you want to ask greenies and start a topic?