I believe you're talking about the ads on kingsnake that look like web pages? Those aren't done easily. It's not just a few lines of HTML code with links to images on Imgur or photobucket. Those ads are linked to their actual web pages and use PHP/SQL along with the HTML to pull the information from databases.
You could make some fancy looking ad out of HTML and link the images to some external image hosting site, but it wouldn't be anywhere close to the easy drag and drop process that you're looking for.
If you're willing to pay to have something set up for you just find an ad/website that you like and ask them who built their website. I think a lot of them were done by Aaron Palmer.
aaronlpalmer@gmail.com
If you want to learn to do it yourself it can be extremely time consuming. It took me many, many hours over several months to get my crappy little website to where it is now. The HTML/CSS is easy. But using PHP/SQL to get information off of the databases and display it on the webpage can be very frustrating to learn. Not to mention setting up the administrator pages where you edit animals. That was a nightmare all on its own.