Finding the original artist

When search/image engines fail, what do you try? Are there any active forums where you can just drop an image and someone replies if they recognise the artist?

I want to find the artists that made these

http://24.media.tumblr.com/tumblr_m4rr1wx1Cj1qbgeseo1_500.png

http://cfile5.uf.tistory.com/image/164B823A4E5F72132B7538

http://iqdb.org/

Also this isn't really what the danbooru forums are for.