I still vividly remember the days when my cousin, an artist, used to spend sleepless nights finishing and painting the ads that some companies ordered from him. Take note those ads are done manually. I used to watch him do it on silk screen most of the time.
But I guess those days are gone. Since most of the companies have websites, you can now actually advertise site on blogs. Just like how some advertisers like LinkFromBlog, a blog online advertising company does.
A simple write up and artwork. Voila! An ad is done!