As a few people have asked, here is my relatively hassle free way of converting any picture of a critter into a silhouette. While I'm using a photograph in this tutorial example, you can use this on basically any digital format picture there is. (Just keep in mind that the idea of the PhyloPic site is all silhouettes appearing on it are copyright free. So you can't go bashing together silhouettes off other people's work. Just your own.)
For my tutorial you're going to need graphic editing software. Sadly it'll have to be something a little more advanced than Paint, but not by much. (I just tried to use Paint, but couldn't find a brightness/contrast control... otherwise Paint does everything I'm about to talk about).
Open your picture in your graphics program. Easy enough, eh ;)
Note: Yeah okay so I'm not doing a prehistoric critter for this tutorial. I just really wanted to be the first to get in a Laughing Kookaburra. So pretend I'm showing you on my previous Tylosaur/Taniwhasaur.
Using your graphic program Brightness/Contrast controls (or at least something that controls the brightness, depending on your specific software) crank the value into the negative hundred(s) level, and you will be done!
So after these two steps you're done!
What, I told you they were easy.
So have fun creating silhouettes, and let's try to populate PhyloPic's with all the weird and wonderful life of the world (past and present).