Weird Browser Pictures on Mac Mavericks
I can not help you further then explained in my answer below.

You have installed a add-on with some "other" software from a 3d party.

That one is causing all your problems.

You can try to talk to the developer, or do a clean uninstall of the application and all its by products on your computer.



Well, it is a bit a spam if you want to call it that way.

When you open that web site and click on it, you will get a browser add on.



When you hover over the "Firefox version" (in my case), you will see following in the bottom left corner:



To get rid of it, open your browsers preferences and remove that add on.

PS:

in my case it shows the Firefox version (add on), since i used it to get the page.

I used the standard os x screen capture for the images in here.

EDIT:

I recommend you get rid off that add-on asap since it installs stuff you do not want!

Also remove all web screen shots taken by that POS! including in your desk top collection.