Interesting....
{opinion}
I'm not sure when Open Clipart Library dropped the "Library" and became more of a social media site. I used to think of it as a good resource for vector images. And I guess the good ones are still there, if you want to search them out. But now, it seems to have become more of an image host (with a lot of really mediocre images).
{/opinion}
However, having said that, doesn't mean I think it's a bad idea. If I were a sketch artist, I might participate. You should make an entry (maybe one of the bull sketches) and include a link to your topic at IF, in the description.
I have used the L-System extension a little bit. I'm not quite sure how it could be used in a drawing called a "sketch" though??
The restriction for me, using L-System, is the need to know, or at least have more knowledge than I do, about the math formulas that are needed. I know, have found, and probably still have local copies of several tutorials that show what kind of formula will draw what kind of shape. And I have tried to....more or less randomly try different formulas, just to see what happens! But I don't have any finished images to show, where I used that extension. (I was trying to make a design that looks like lace - old topic at IF, search "lace")