This is awesome man!
I love Robin Williams, so my critique is obviously not towards the content.
I respect that you wanted to do a tribute and that's very nice. The line work you do is usually pretty clean, in this piece, areas like the hands could be cleaned up a bit. Also the way you chose to crop certain areas is awkward. For example the Robin Hood's feet or the center figure's hands. I can assume maybe you did this quickly and on purpose due to some areas having line-weight, but I can't know for sure :/
I've seen your process and it can definitely get meticulous and detail oriented, so it's just a bit ironic that you chose to make it look like this on content you seem to care a lot about.
Out side on that little bit, this definitely deserves Front Page and honestly would love to see a bit more art n here attributed to him.