Ack! I almost wet myself just now, after realizing that tons of Ernst Haeckel illustrations are available in high-res, in the public domain, on Wikipedia. I am downloading them now. I’m going to cycle through them for my desktop background. And someday I am going to make them into wallpaper prints. (You know, when I get some walls.) Seriously, can you imagine??
If you’d like a zip file of all the Haeckel images I downloaded, you can get it here. It’s 187 MB, 121 images.