This is fantastic, there is a great attention to detail and I like the highlight surrounding him. The background may be just a concrete texture but I can forgive you for the work put into this (Heard you mention it in the video too). I've got to also complement you on drawing Salad Fingers and being a fan of David Firth as I love his work as well.
I also watched your speedpaint video, I was surprised to see a personality as the artist and narration through a portion of it due to the fact that most videos just have music. I would imagine that you took inspiration from David Firth with the way you were acting in the video and I also found to be kind of cringe worthy (sorry) but it was fun nonetheless.
I look forward to seeing more from you and hope that this will bring you a decent amount of attention from newgrounds users for being a great artist. One last thing is that you should probably link your youtube/deviantart/other on newgrounds so people can go there as well.